Cost-benefit analysis of Costco Anywhere Visa Card
Published:
As the year-end approaches, it is time to perform a cost-benefit analysis of my credit cards. Here I discuss the Costco Anywhere Visa Card.
Blog posts
2025
Nissan Leaf after 7 years (3)
Published:
In this post and this post, I discussed my ordeal of getting the battery of the Nissan Leaf replaced. This matter was resolved in September 2023, but since I have never posted an update, here it is.
529 qualified expenses
Published:
I opened 529 accounts for my kids about 15 years ago. Their nominal balances have grown by about 200% over this period. (Actually, this is something that I regret. I enrolled in targeted date funds without thinking too much. Investment returns have suffered since 2020 because the portfolio’s bond share increased and inflation was high. I should have invested 100% in stocks instead.)
Is it worth keeping the Marriott Bonvoy Boundless Card?
Published:
As I occasionally use Marriott, a few years ago I got the Marriott Bonvoy Boundless Card because it was offering a welcome bonus. I won’t go into details, but the basic structure is that the annual fee is $95 and the benefits are 6 Marriott Bonvoy points per dollar spent on Marriott stays and an annual Free Night Award (worth up to 35,000 Marriott Bonvoy points). The value of a Marriott Bonvoy point is about 0.8 cents. (Regardless of the credit card use, Marriott Bonvoy members earn an additional 10 points per dollar spent on stays. As an automatic Gold Member with the American Express Platinum Card, I get a 25% bonus, so 10 points become 12.5 points. But these points are not included in the above calculation because they are independent of the credit card.)
Buying Delta gift card with American Express Delta SkyMiles Platinum Card
Published:
With my American Express Delta SkyMiles Platinum Card, I received a targeted offer for 5 extra Delta SkyMiles per dollar for purchasing a Delta gift card. In addition, Delta is also running a promotion with a $25 Uber voucher for those who buy $300 or more in Delta gift cards.
Tracking spending
Published:
In this post, I mentioned that Fidelity Full View provides account syncing for Fidelity customers. Dividing spending into categories, it also presents a pie chart of spending. The picture below is my own example; I erased the specific amounts and kept only the percentages. In general, to save money, it is best to focus on spending categories with large shares, which in my case are home, children, food, travel, etc.
Tracking cash flow
Published:
In this post, I mentioned that I tracked every single penny of my spending from 2008 to 2022, but I stopped because there was little room left to improve my behavior, and the opportunity cost of keeping track of everything was too high. During this period, I tracked my income and expenditures by manually entering items in an app and using (now discontinued) Mint.com.
American Express Blue Cash Preferred card (2)
Published:
In this post in March, I discussed the reward structure of the American Express Blue Cash Preferred card. Here is a quick review. The annual fee is $95. The cash back structure is as follows.
Capital One Quicksilver 0% intro APR (3)
Published:
In my post, I mentioned that I have been happy with the Capital One Quicksilver Card because it offered 0% intro APR for 15 months (and the card has no annual fee and gives 1.5% cash back on all purchases).
I referred my wife to open an account, and we both received the referral bonus. But what has been truly great is the targeted deals through Capital One Shopping. We are now remodelling our two bathrooms that are over 20 years old. As my wife has been searching for fixtures, she has started receiving targeted deals from Home Depot, Lowe’s, Bed Bath & Beyond, etc., often offering 15% cash back. Furthermore, the timing of our remodelling coincided with Black Friday/Cyber Week sales (of course, intentionally), so we often get an additional 20% off from the merchants. Overall, I think we saved a few thousand dollars by optimizing credit card use.
I highly recommend the card to anybody. If you open an account by clicking this link, you will receive an extra sign-up bonus.
Saving taxes through UTMA accounts
Published:
While studying how to legally save on taxes, I realized the following trick.
- Transfer appreciated stocks to your child’s UTMA (Uniform Transfers to Minors Act) custodial account.
- Sell the stock while keeping the capital gains within $1,350.
- Use the fund in whatever way you like.
This procedure completely avoids capital gains tax (15% at my tax bracket). The reason is that the standard deduction for a child is $1,350, so as long as income is below that amount, there is no need to file or pay taxes.
I wish I had known about this trick earlier, but it’s better to learn about it later than never. As I have substantial shares of VTI that I bought in 2010 for $60 per share but are now valued at around $335, I transferred a few shares to my kids’ UTMA accounts and sold them. Turning appreciated stocks into cash is almost alchemy.
Round trip between San Diego and Atlanta
Published:
I often fly between San Diego and Atlanta, usually with Delta (because there are more flight options than Alaska, which also offers direct flights between SAN and ATL). As I was looking to book my next trips, I noticed that flight tickets got much more expensive, often over $600 round-trip with Delta (main cabin). After playing around with various searches, I realized that if I book a round trip from Atlanta instead of from San Diego, the price drops by 25% or more. I am not sure why, but maybe it’s because if I book from Atlanta and the trip is over the weekend, the booking system may classify me as a (price-elastic) leisure traveller. By using Alaska instead of Delta, the price often drops below $300 round-trip. Although I have achieved gold status with Delta, since Alaska is much cheaper and also offers status match, I will likely switch to Alaska.
Econ Journal Watch goes LaTeX
Published:
Great news. Starting from the September 2025 issue, Econ Journal Watch publishes papers typeset in LaTeX.
For years, I have been begging the editorial board of EJW to accept LaTeX submissions. This summer, I attempted to submit a comment to urge EJW to accept LaTeX submissions, but to my surprise, I was told EJW was working to transition to LaTeX over the summer, so the point of my comment became moot. The call for papers does not appear to have been updated yet, but we will see whether they officially announce that they welcome LaTeX submissions.
American Express increased annual fee of Platinum Card to $895
Published:
American Express increased the annual fee of the Platinum Card from $695 to $895.
In this post last year, I discussed my love-hate relationship with the American Express Platinum Card. When I opened the account many years ago, I recall that the annual fee was $450. Then it increased to $550 and then to $695. Now it’s $895. It has reached a point where I need to reconsider whether it is worth keeping the card. (See also this opinion.)
The card offers various credits, but most are things I won’t use or are redundant.
- $400 Resy credit ($100 quarterly): Most of the restaurants that I go to anyway (Asian food) are not in Resy. To me, it makes the most sense to use Resy restaurants for business (for which I get reimbursed) and get the credit, but optimizing is a mental burden.
- $600 Hotel credit ($300 semiannually): This is for Fine Hotels + Resorts or Hotel Collection, and you need to stay for two nights. Most hotels are expensive. If I can use it for business trips (for which I get reimbursed), it is worth it, but I won’t stay at these hotels for personal trips.
- The American Express Global Lounge Collection: This is a benefit I have valued in the past (to get free food, drinks, and space at airports, especially Centurion Lounges). But now that I have achieved Delta Gold status (I also have One World Emerald status), its value has declined relatively.
- $200 Uber credit: This is useful when I travel. During the off-season, I have to use it for Uber Eats. (Uber Eats is overpriced to begin with, so I usually order one Indian curry for pick up on Uber Eats and then order extra stuff at the restaurant directly.)
- $120 Uber One Credit ($10 monthly): The cost of Uber One is $9.99 per month, so essentially it’s free. I have just signed up for this service, so I will see whether it’s useful.
- $300 Digital Entertainment Credit ($25 monthly): This is useless. I don’t use these kinds of services.
- $200 Airline Fee Credit: I use it for Delta, and in the past, it helped me cover change fees or upgrades. But it’s not really necessary.
- $209 CLEAR Plus credit: CLEAR used to be useful for skipping the security line at the airport. But TSA Precheck has improved (with digital ID, etc.), and I no longer see value in CLEAR.
- Hilton Honors Gold Status: You get free breakfast for two people, but I rarely stay at Hilton.
- Marriott Bonvoy Gold Elite Status: I have a different Marriott card, so this is redundant.
- Leaders Club Sterling Status from The Leading Hotels of the World: I have never heard of this hotel chain.
- Fee Credit for Global Entry or TSA PreCheck: This is useful, but I have two other cards that provide the same benefit, so it is redundant. (I can use it for family members, though.)
- $300 Lululemon credit ($75 quarterly): My wife and daughter buy stuff at Lululemon sometimes, so it could be useful.
- $100 Saks Fifth Avenue credit ($50 semiannually): I won’t shop at Saks unless there is this credit. I just buy minimal stuff, like underwear, when it’s on sale.
- $200 Oura Ring credit: I don’t know what this crap is.
- Walmart+ Monthly Membership credit ($12.95 monthly): I don’t use it.
I didn’t list all the benefits and credits, but the rest are less important. My membership renewal is next May, so I still have time to think about it.
Slavery descendants to get preference for college admission if bill approved
Published:
This is utterly absurd. The California Assembly Bill 7 states
This bill would state that the California State University, the University of California, independent institutions of higher education, and private postsecondary educational institutions may consider providing a preference in admissions to an applicant who is a descendant of slavery, as defined, to the extent it does not conflict with federal law.
As a classical liberal, I believe that whether you should be admitted to college or not depends only on your merit, and who your ancestors were has no relevance. Besides, how do you even verify whether one of your ancestors was a slave?
The radical left has often promoted discrimination under the name of DEI. This one has the same intention, though it is carefully worded (“may consider providing a preference […] to the extent it does not conflict with federal law”) so as not to be legally binding.
Econ Journal Watch comment leads to retraction
Published:
Econ Journal Watch (EJW) is one of my favorite journals, which publishes critical comments. I have published one myself.
While browsing past issues of EJW, I came across this comment, which documents that the 2017 Accounting Review article of Bird and Karolyi reports exactly identical numbers in all 11 tables as the 2015 working paper version, despite the fact that the authors switched the main specification and the robustness check between the working paper version and the published version. To this comment, Bird and Karolyi replied
we identified a potentially confusing description of our methodology, which was introduced during the final iteration of copy editing at The Accounting Review. This description conflicted with our correct and clear description of our methodology elsewhere in the published version of the paper.
Out of curiosity, I checked the original published article, and the publisher simply states
The authors acknowledged that the published version of their article misstates the use of CRSP-based index membership in the main specifications and Russell-based index membership data as a robustness test. […] However, the authors were unable to provide the original data and code requested by the publisher that reproduce the findings, as shown in the article’s tables, supporting this assertion. Accordingly, the article has been retracted.
I am glad to know that some journals do the right thing.
Number of articles on arXiv
Published:
Since 2017 or 2018, I have only posted my working papers on arXiv because it is free, open to anyone (they need a referral for initial submission, though), users can download the source file, and version control is straightforward. I see no value in SSRN, though it still seems popular among economists. An added bonus of arXiv is that if you use Overleaf, there is an option to submit to arXiv, so the submission process is (mostly) painless.
Out of curiosity, I wanted to know how many articles arXiv publishes by year and field. It was easy to get these statistics. For instance, for economics, you can go to https://arxiv.org/archive/econ and click “Article statistics by year”.
The graph below shows the number of articles in mathematics (math), computer science (cs), physics (physics), statistics (stat), and economics (econ). Here are a few observations.
- Mathematics, physics, and statistics seem to have a common trend.
- Computer science was not special until around 2004, but since then, the number of articles has grown much faster than in other fields.
- Economics is still very small but is growing more rapidly than other fields (except computer science).
- There seems to be a slight increase in the number of articles in 2020, likely because people had more time to do research during the pandemic or because it became popular to write papers on COVID.
Capital One Quicksilver 0% intro APR (2)
Published:
In my post, I mentioned I opened the Capital One Quicksilver Card because it offered 0% intro APR for 15 months (and the card has no annual fee and gives 1.5% cash back on all purchases).
I have been using the card for about half a year, and so far I am very happy with it. In particular, I paid my federal and state income taxes using the card, so I essentially deferred the tax payment by one year, interest-free. (The IRS charges a 1.75% fee for paying taxes with a credit card, but because the card gives 1.5% cash back, it is nearly offset.) I highly recommend the card to anybody. If you open an account by clicking this link, you will receive an extra sign-up bonus.
On illegal immigrants
Published:
If a person enters my house without my permission, I suppose I have the right to ask them to leave, and if they refuse, I may force them to leave. By analogy, if a person crosses the border into a country without the government’s permission, I suppose the government has the right to ask the person to leave, and if they refuse, they may force them to leave. Therefore, I see no problem with some governments cracking down on illegal immigration and attempts to deport illegal immigrants (although there may be exceptions on an individual basis, for example, children who were taken to the country by their illegal immigrant parents and grew up for quite some time, losing ties to their country of birth). It is just common sense, following from the fundamental principle of a liberal society that honors property rights. A corollary of this argument is that I do not understand why some people (typically the radical left or whatever they are called) organize protests against the crackdown on illegal immigration.
夏目漱石全集
Published:
だいぶ前の話になるけど、アトランタへの通勤の時間を有効に使おうと思って、Amazon Kindleで夏目漱石全集を2ドルだか3ドルで買った。主要作品は文庫本で持っているけど、マイナーな作品も読めてとてもよかった。
Is WTN necessary?
Published:
Among amateur tennis players, including high school and college players, I think it is fair to say that UTR (Universal Tennis Rating) is the number that we look at to measure the skill level. UTR rates tennis players on a scale of 1 to 16.5, with higher numbers indicating a higher skill level. According to the Wikipedia page, UTR was developed by a private company in 2008 to evaluate junior players.
The case for flat tax
Published:
My tax situation in 2024 was very complicated due to a job change, a move, and a Roth conversion, among other factors. While filing for taxes, I studied part of the tax code. I discuss my thoughts here.
American Express Blue Cash Preferred card
Published:
Last year, I analyzed the costs and benefits of a few credit cards in this post. Recently, I noticed benefits to the American Express Blue Cash Preferred card that I was not previously aware of, so let me provide an additional analysis.
Everyday Millionaires
Published:
During my recent flight, I read Everyday Millionaires by Chris Hogan. The same Google Feed article on personal finance that I mentioned in my earlier post also recommended this book, and I borrowed it from the library at the same time as Baby Steps Millionaires by Dave Ramsey.
Baby Steps Millionaires (2)
Published:
In my article yesterday, I discussed the book Baby Steps Millionaires by Dave Ramsey. This book presents many real-world examples of ordinary people achieving financial independence (“millionaire” status) through hard work, discipline, and consistent investing. These stories are all inspiring.
Baby Steps Millionaires (1)
Published:
This weekend, I read Baby Steps Millionaires by Dave Ramsey. I came across this book because a Google Feed article on personal finance recommended it. I could have clicked “Buy Now” on Amazon ($18 or so), but I found it in a local library’s catalog, so I went to the library to borrow the book. As I discussed in my article on frugal habits, if I account for the opportunity cost of spending 20 minutes to visit the library, it does not make economic sense. But to me, visiting the library is part of leisure, so it is justified.
Temptation of Capital One Quicksilver 0% intro APR
Published:
In my recent post, I discussed the cost-benefit analysis of credit cards.
Yield on UCSD pension
Published:
As I was preparing to file taxes, I paid some attention to my UCSD pension balance. When I quit UCSD last year, I left the pension there rather than cashing it out. It occurred to me to evaluate the pension’s yield, so I made some calculations.
The Algebra of Wealth
Published:
I recently read The Algebra of Wealth by Scott Galloway. An article about it came up in my Google Feed, and the book looked interesting, so I borrowed it from the library. (I could have clicked “Buy Now” on Amazon as it costs less than $20, and I could have used my research fund, but I am frugal.)
My frugal habits
Published:
Living a frugal life is one of the most important means to achieve financial independence. In this post, I will discuss tips for frugality.
The Richest Man in Babylon
Published:
Over the winter break, I read The Richest Man in Babylon, which is a 1926 classic on personal finance. I have read it a few times before, but it is entertaining enough to read once every few years. I highly recommend it to anyone interested in personal finance. But let me mention that the book is more philosophical or theoretical than practical, and to succeed in personal finance, it is important to augment abstract knowledge with practical tips, such as understanding the tax code.
2024
Farewell, Citibank
Published:
As part of my annual financial review, I closed my Citibank checking account, which I have had since coming to the U.S. in 2008.
Cost-benefit analysis of credit cards
Published:
As year-end approaches, I downloaded the transaction history for my credit cards to analyze the costs and benefits.
Essential Mathematics for Economics
Published:
My textbook, Essential Mathematics for Economics, is now published and sold at Amazon. It would be nice if somebody could write a review.
Submission fee at Journal of Monetary Economics
Published:
Recently, I thought about submitting a paper to Journal of Monetary Economics. Upon reading its submission guideline, I learned that they charge a submission fee of USD 350, which I found quite expensive.
Syllabus template
Published:
As I prepare for my first teaching assignments at Emory, I have started by creating a syllabus template. My department provided a Word template, but it wasn’t exactly to my taste, so I wrote a \(\LaTeX\) template here. The version titled syllabus_template.tex follows the basic structure of the Emory economics template, and the version titled syllabus_template_toda.tex adds some of my information that I use across all my courses. A few comments:
Income inequality at UCSD economics, 2023
Published:
The compensation at University of California has just published the figures for 2023. I have updated the data set for my paper and run regressions. In case readers are interested in predicting their salaries, the prediction equation in 2023 is \[\log y = 12.12 -0.0100T + 0.0052N_\textrm{pub} + 0.0204N_\textrm{top5} + 0.2485D_\textrm{assoc} + 0.5048D_\text{full}, \] where \(y\) is the 9-month salary, \(T\) is the number of years elapsed since obtaining Ph.D., \(N_\textrm{pub}\) is the cumulative number of peer-reviewed research articles, \(N_\textrm{top5}\) is the cumulative number of top 5 publications, and \(D_\textrm{assoc}, D_\textrm{full}\) are dummy variables for associate and full professors.
Comparing taxable, traditional, and Roth accounts
Published:
Three years ago, I wrote a blog post in which I mentioned that I stopped (strictly speaking, significantly reduced) contributing to 403(b) and 457(b) retirement savings plans because I could no longer afford it.
Nonexistence of Rational Bubbles in Miao and Wang (2018)
Published:
Jianjun Miao of Boston University and Pengfei Wang of Peking University published a paper titled “Asset Bubbles and Credit Constraints” at American Economic Review in 2018. In their abstract, they state that they “provide a theory of rational stock price
bubbles”. For those who are not familiar with the economic theory of bubbles, “rational bubble” means that the asset price (denoted by \(P\)) exceeds its fundamental value (denoted by \(V\)) defined by the present value of dividends, so \(P>V\), in a model in which agents are rational.
Most papers in the rational bubble literature assume that the asset pays no dividends, because there are known difficulties with positive dividends. (I can talk about this more, but it is technical, so I refer the reader to my JME review article with Tomohiro Hirano, especially Section 3.4.) Miao and Wang’s paper is ambitious because they claim to attach a rational bubble to a dividend-paying asset. For instance, in their literature review, they state
Some studies (e.g., Scheinkman and Weiss 1986; Kocherlakota 1992, 2008; [Santos
and Woodford 1997](https://doi.org/10.2307/2171812); Hellwig and Lorenzoni 2009) have found that infinite-horizon models of endowment economies with borrowing constraints can generate rational bubbles. Unlike this literature, our paper analyzes a production economy with stock price bubbles attached to productive firms.
Here, the cited papers are all rational bubble models. Subsequent papers by the authors also advertise Miao and Wang (2018) as a rational bubble model. For example, Footnote 4 of Dong, Miao, and Wang (2020) states
Introducing dividends or rents will complicate our analysis without changing our key insights. See Miao and Wang (2018) and Miao, Wang, and Xu (2015) for models of rational bubbles attached to assets with dividends or rents.
In a recent working paper by Tomohiro and I titled “Rational Bubbles: A Clarification”, we mathematically proved the nonexistence of rational bubbles in the model of Miao and Wang (2018). In other words, \(P=V\) in their model.
It seems that there is a widespread misunderstanding in the literature. According to our systematic literature search detailed in the paper, 74 papers focus on the theory of bubbles and cite Miao and Wang (2018) as a paper on bubbles. Among those 74 papers, 68 cite Miao and Wang (2018) as a rational bubble model specifically. As proved in our paper, the model of Miao and Wang (2018) is not a rational bubble model. It is an asset pricing model with multiple equilibria, in which the high- or low-stock price equilibrium is selected based on agents’ self-fulfilling expectations. In both equilibria, the stock price reflects fundamentals. I hope that our paper will help foster a better, mutual understanding of bubbles and that the science of bubbles will prosper forever, without ever imploding.
Backdoor Roth
Published:
I have been investing in a Roth IRA. Currently, the contribution limit is $7,000/year.
I haven’t been paying attention much, but there are income limits for traditional and Roth IRAs. For traditional, married couples filing jointly cannot deduct contributions if their modified adjusted gross income (MAGI) is above $136,000. For Roth, married couples filing jointly cannot contribute if their MAGI is above $240,000.
Because I recently got a raise by changing employers, I can no longer contribute to a Roth. However, there is a legal loophole known as the backdoor Roth. All you need to do is contribute to a traditional IRA (which is not tax-deductible due to the income limit, but that is irrelevant), then do a Roth conversion. This way, anybody can contribute to a Roth regardless of their income. So from next year on, I can simply contribute $7,000 of cash to my traditional IRA account, do a Roth conversion, and invest the funds in whatever way I like.
However, this year there is a problem because I have already contributed to a Roth IRA before I knew I would exceed the income limit. I did a bit of research and found this article. Reading it, I did the following.
- First, I recharacterized this year’s Roth contributions to traditional.
- Then, I contributed cash to a traditional IRA to hit the annual contribution limit.
- Finally, I converted all funds from traditional to Roth.
The idea is that, by recharacterizing my existing Roth contributions to traditional, it’s as if I contributed to traditional in the first place. To save my mental resources, I added enough cash to hit the $7,000 annual contribution limit right away, so I can forget about it for this year. Because the existing contributions to Roth had capital gains, by recharacterizing to traditional, I will have to pay capital gains taxes. This TurboTax article explains how to handle taxes.
It’s fun to learn new money tips, but I spent a few hours doing so. Since the income limit for Roth is not binding due to the backdoor Roth loophole, it would make more sense for the government to simply eliminate the income limit for Roth altogether. And if there is no income limit for Roth, there should be no limit for traditional either. Our lives will be much simpler that way.
Farewell, UCSD
Published:
As I have already announced on my website, I am resigning from UCSD. Today is my last day. I have been employed for 11 years, so I have bittersweet feelings for sure.
Trip to Japan
Published:
I have just returned from a 10-day trip to Japan. During this short stay, I visited the Ikaho hot spring, did some sightseeing in Tokyo with my family, and gave talks at Waseda University and the University of Tokyo.
Last talk at UCSD
Published:
I presented my paper “Housing Bubbles with Phase Transitions” at the UCSD Friday faculty seminar. Because this was my last talk at UCSD, I gave the following speech.
Website updated
Published:
After spending several days, I significantly updated my website. Below is a list of the main changes.
- Previously, there was a “Research” page that I created manually. But it was tedious to list all papers in a consistent style (e.g., journal names in bold, coauthors in italics, etc.), so I automated it.
- I omitted publication information except the journal name and year, because I don’t think they are very important, and one can easily find them by clicking the link to the published paper.
- I searched for all my paper drafts on my computer and added slides whenever I found them.
- I merged “Conference proceedings” with “Other publications” because I don’t see a reason to keep proceedings as a separate section, given that I don’t have many.
Talks
Published:
Maybe it is not the best use of my time, but I created a “Talks” page, which lists past and future talks and presentations. After spending all afternoon tweaking the code, I came up with something satisfactory. For now, I included only talks in 2023 and 2024, but I might add past ones.
Essential Mathematics for Economics
Published:
I finished writing the draft of my forthcoming textbook “Essential Mathematics for Economics”. The book is based on my math camp teaching material. Please let me know if you have any comments on the draft.
2023
Nissan Leaf after 7 years (2)
Published:
I have been waiting almost 9 months for the replacement battery for my 2016 Nissan Leaf, and the delay is extremely frustrating.
Nissan Leaf after 7 years (1)
Published:
In 2016, I purchased a Nissan Leaf. Given the technological progress in electric vehicles, it’s almost a joke now, but it had a 30kWh battery with around 110 miles of range. Including everything (tax, registration, etc.), it cost 42,647 dollars. My employer subsidized $10,000, and I received a $7,500 federal tax credit, so at that time, I thought it was not a bad deal. 110 miles of range seemed enough for daily chores, and for road trips, we had been renting a gas-powered vehicle. This was our only vehicle in the household until 2020, when we bought a Tesla Model Y.
biblatex
Published:
For managing bibliographies for my papers, I have been using the natbib package with bibtex for a long time.
2022
Pitfall of electric bike
Published:
When I moved from Connecticut to San Diego in 2013, one thing I paid attention to when searching for a house was finding one within a reasonable distance from work. I knew that San Diego had nice weather and commuting by bicycle was feasible. So to save money and get some exercise, I cut the number of vehicles in my household from two to one and bought an electric bike to commute. (In 2020, I went back to two vehicles because we could no longer keep up with only one vehicle to manage kids’ activities.)
Wimbledon banning Russian players is discrimination
Published:
It was reported that Wimbledon will ban Russian (and Belarusian) players because of Russia’s invasion of Ukraine.
2021
Investment and taxation
Published:
Since I started working in 2013, I haven’t given much thought to investing. Because I know that investing in an index fund is the theoretically right thing to do and I do not like paying taxes, in addition to participating in my employer’s mandatory defined benefit retirement plan, I have just been maxing out investments in 403(b), 457(b), and Roth IRA (all invested in low-cost index funds).
Optimal use of sabbatical credit
Published:
This post is completely boring for outsiders. I am just writing this down so that I do not forget.
Disabling Canvas Inbox
Published:
My university uses Canvas for instructional purposes. Canvas has a feature called “Inbox” that lets you send messages. I have long thought this functionality not only useless but even harmful. This is because I ignore everything sent to Canvas Inbox, but students who are unaware that I do not use it may send me messages that get ignored and then complain. Since I was unable to find information on how to disable Canvas Inbox, I contacted the university’s technical support.
Shan Xi Magic Kitchen overcharged tip
Published:
I have been a long-time customer of Shan Xi Magic Kitchen, a Chinese restaurant in San Diego that serves Shanxi cuisine.
Fun facts about tennis rule (3)
Published:
These days, I mostly play competitive tennis, so my opponents usually have a good understanding of the rules, and we do not get into disputes. However, debates and disputes sometimes occur in recreational play, which could be annoying. So, in a series of posts, let me talk about some rules that could be overlooked by recreational players. The official rules can be found in the “Friend at Court” here.
Fun facts about tennis rule (2)
Published:
These days, I mostly play competitive tennis, so my opponents usually have a good understanding of the rules, and we do not get into disputes. However, debates and disputes sometimes occur in recreational play, which could be annoying. So, in a series of posts, let me talk about some rules that could be overlooked by recreational players. The official rules can be found in the “Friend at Court” here.
Fun facts about tennis rule (1)
Published:
These days, I mostly play competitive tennis, so my opponents usually have a good understanding of the rules, and we do not get into disputes. However, debates and disputes sometimes occur in recreational play, which could be annoying. So, in a series of posts, let me talk about some rules that could be overlooked by recreational players. The official rules can be found in the “Friend at Court” here.
Capital and labor income Pareto exponents
Published:
My paper “Capital and Labor Income Pareto Exponents across Time and Space” was accepted for publication in Review of Income and Wealth. I have long felt that in discussions of inequality, people often fail to distinguish between income and wealth. In this paper, we (my coauthor Tjeerd de Vries and I) estimate the Pareto exponents for capital and labor income separately for as many countries/years as possible. Using 475 country-year observations, we find that the median capital and labor income Pareto exponents are 1.46 and 3.35, respectively, so capital income (hence wealth) is more unequal than labor income. This conclusion is not surprising at all, but the point of the paper is to provide a systematic analysis, which was lacking in the earlier literature.
Paper accepted
Published:
My paper “Asymptotic Linearity of Consumption Functions and Computational Efficiency” with Qingyin Ma has been accepted for publication in Journal of Mathematical Economics. The main result is that when the marginal utility function is regularly varying (behaves like a power function), the consumption function in the optimal savings problem becomes asymptotically linear, and we characterize the asymptotic slopes. Initially, this paper was part of a larger project with Ma & Toda (2021), but we split it into two to keep them focused and at manageable lengths. The JET paper treats only the case with CRRA (constant relative risk aversion) utility, but it has an economic application. The JME paper assumes regular variation, along with some technical conditions, and discusses computational efficiency.
Won tennis tournament
Published:
I played the San Diego District Championship NTRP 3.5 men’s singles over the last two weekends, and I won the final 6-1, 6-7(5-7), 7-5.
Paper accepted
Published:
My paper “Perov’s Contraction Principle and Dynamic Programming with Stochastic Discounting” was accepted for publication in Operations Research Letters. I found a generalization of Banach’s contraction mapping theorem while studying a certain dynamic programming problem with stochastic discounting. It turned out the fixed point theorem was due to Perov (1964), but I found the application interesting, so I wrote a short paper.
Good pusher, bad pusher
Published:
In tennis, a pusher is a player who can consistently hit the ball back inside the opponent’s court. They have good footwork and run to every ball. Michael Chang and Rafael Nadal are legendary professional players who have perfected this valuable skill.
What junior tennis and publishing papers have in common
Published:
I have been playing tennis and publishing papers long enough to find something in common.
American Home Shield is fraudulent
Published:
I have been a customer of American Home Shield, a home warranty company, for a few years until today. This company is the worst business I have ever dealt with, I would say worse than the California Department of Motor Vehicles.
Fun drill to improve consistency in tennis
Published:
I have been a recreational tennis player for 6 or 7 years. Since fall 2020, I have started to play some matches. (You can see my statistics here.)
Full-text articles on ResearchGate
Published:
I don’t remember when I opened a ResearchGate account; I guess I did so to increase the visibility of my research. I don’t really use their service, but I find it annoying that I get requests to upload full-text articles. This is a waste of time because most of my papers are available online as working paper versions. (These days I upload my working papers exclusively to arXiv.) So I decided to write a short document stating that all of my papers are linked from my personal website (and provided the link), and uploaded it as a full-text article.
GPIF Award
Published:
It is a great honor to announce that I have been awarded the 4th Government Pension Investment Fund (GPIF) Finance Award under the auspices of Ministry of Health, Labor and Welfare and Ministry of Education, Culture, Sports, Science and Technology in Japan. I am very happy that my research has been recognized.
Homothetic theory of the saving rate of the rich
Published:
My paper “A Theory of the Saving Rate of the Rich” was accepted at Journal of Economic Theory. I started this project in early 2020. Initially, the paper was about rigorously establishing the asymptotic linearity of policy functions when preferences are homothetic and the constraint is asymptotically homogeneous of degree 1. This is not surprising but the proof is difficult. As we worked on the proof, we (my coauthor and I) discovered that the asymptotic slope of the policy function can be zero, which was surprising. When the asymptotic marginal propensity to consume (MPC) is zero, an infinitely wealthy agent saves 100% of the wealth, which can explain the empirical puzzle that wealthy people save a lot although it seems unnecessary. So instead of focusing on just a mathematical fact, we decided to frame the paper as a new theory of the saving rate of the rich.
Financial lesson from 2020
Published:
I have been investing for over 20 years. After learning about the capital asset pricing model and the mutual fund theorem, and after reading “A Random Walk Down Wall Street” and “Stocks for the Long Run”, I have been investing in low-cost index ETFs such as VTI and VXUS. This allowed me to stay in the market during the bottom in March 2009 and not miss the bull market since then, despite some of my colleagues advising me that stocks were overpriced. My kids’ 529 funds have grown about 3 times in nominal value. I have been maxing out my 403(b), 457(b), and Roth IRA contributions, and joking that I could retire if I choose to. Based on theory and experience, I preach the importance of passive investing to students in my finance class.
2020
Necessity of HARA for the concavity of consumption functions
Published:
My paper “Necessity of Hyperbolic Absolute Risk Aversion for the Concavity of Consumption Functions” was accepted at Journal of Mathematical Economics. The publication process was quite efficient. I came up with the idea in late September 2020 and wrote a short paper. After being rejected by another journal, I submitted to JME. I am very happy that it came out in less than three months after I started the project. Journals in economics tend to be very slow in the review process, perhaps because many papers are long and unfocused. We should all write concise and focused papers.
Great Barrington Declaration
Published:
I have just signed the Great Barrington Declaration.
My unpublished COVID-19 paper is now my most cited paper
Published:
Recently, my working paper Susceptible-Infected-Recovered (SIR) Dynamics of COVID-19 and Economic Impact has surpassed my JEBO paper in terms of citation counts, and has become my most cited paper. My COVID-19 paper is one of the very first written by an economist on this topic, and it appeared in the first issue of the working paper series Covid Economics. Although I am no longer working on this paper since the situation with COVID-19 has been changing too quickly (especially when I wrote the paper in March 2020) to keep up with, I am glad that this paper has made some impact. In fact, it was featured in VoxEU and Fortune articles.
Berkeley banning junk food in checkout aisles is nonsense paternalism
Published:
As a long-time California resident, I am very well aware of all that government red tape. But the recent move of the city of Berkeley to ban placing junk food and beverages at checkout aisles is completely nonsense.
Difference between $$..., \[..., and \begin{equation*}...
Published:
I have been using \(\LaTeX\) for over 20 years now. When I write a displayed equation without numbering on a single line, I have been using $$...$$ because it was simple. I didn’t understand why some people use \[...\], since the latter takes longer to type and isn’t necessarily easy to read. Today I read this article and learned that $$...$$ is incorrect. From now on, I will switch to \begin{equation*}...\end{equation*} because it is easy to read and we can add equation numbering by deleting * if we change our mind.
Naming things after each other
Published:
I have recently read the article “Why Mathematicians Should Stop Naming Things After Each Other”. The same logic seems to apply to economics.
Inequality on spectral abscissa
Published:
Let \(A, B\) be square (complex) matrices such that \(|B| \le A\). Then it is well known that \(\rho(B) \le \rho(|B|) \le \rho(A)\), where \(\rho\) denotes the spectral radius (largest absolute value of all eigenvalues). See, for example, Theorem 8.4.5 of Horn and Johnson (2013). In my recent paper with Brendan Beare and Won-Ki Seo, we needed to use the spectral abscissa (largest real part of all eigenvalues) instead of the spectral radius. By analogy, we can make the following conjecture: if \(A, B\) are square complex matrices such that \(\mathrm{Re} b_{nn} \le a_{nn}\) for all \(n\) and \(|b_{nn’}| \le a_{nn’}\) for all \(n \neq n’\), then is it true that \(\zeta(B) \le \zeta(A)\), where \(\zeta\) denotes the spectral abscissa?
White rice and brown rice
Published:
There is a restaurant called “The Bistro” on the UCSD campus. Although I don’t like this restaurant because it’s basically a fusion American-Asian place, sometimes I have to eat there when we take seminar speakers to lunch. Once I ordered some fried cod (neither quite fish and chips nor tempura). On the menu, it said the dish came with brown rice, so I asked the server to substitute white rice. (Although I don’t have statistics to quote, I would say most Japanese people eat white rice - only those that are health-conscious and opinionated eat brown rice, though obviously the latter is healthier.) When the dish arrived, I was stunned that the rice, though white, was sushi rice (i.e., vinegared rice). I asked the server to bring proper white rice, but she didn’t know the difference. Since then, whenever I organize the seminar lunch, I choose a different place.
Created new website
Published:
I have created a new website. I have been using Google Sites to create my old website. I like the classic Google Sites because it lets users take control of the structure by programming in HTML. However, the new Google Sites no longer have this feature, and since the classic Google Sites will be discontinued in 2021, I had to find another solution. After a bit of Google search, I found this template, which is exactly what I wanted (ability to take full control, free, no advertisements, etc.).