There are peaks, there are valleys, and sometimes you’re just stuck at the bus stop a bit longer.

I knew, and was heavily influenced by a fascinating AER paper by Joel Waldfogel from 1993, aptly titled “The Deadweight Loss of Christmas.” Economists often praise holiday spending for its positive macroeconomic effects. However, gift-giving’s critical microeconomic facet lies in the recipient making different choices than the giver. Essentially, gifts risk being mismatched with recipients’ preferences, potentially causing a deadweight loss. Waldfogel’s paper, deriving data from Yale undergraduates’ surveys, estimates holiday gift-giving destroys 10% to 33% of gifts’ value. While these students might not represent the entire U.S. populace, their gifts’ nature likely does. Annually, holiday expenditures hit $40 billion, implying a substantial deadweight loss, rivaling income taxation’s inefficiency. The paper also explores cash gifts versus in-kind gifts, determining friends and “significant others” give the most valued gifts. ...

People straddling the realms of economics and computer science have a fascinating way of thinking. I used to believe I was the sole individual who viewed my surroundings through a “math” filter. However, it appears that everyone in this field has their unique quirks. Take, for instance, one of the professors I work with. He genuinely “calculates” his academic networking social distance. Our recent discussion about a paper left him in awe of the mathematical techniques employed, and here’s the conversation: ...

Regarding ADIP, a first-order method for solving LP, the following is an excerpt from Deng et al.’s arxiv page: The ADMM-based interior point method (ABIP, Lin et al. 2021) is a hybrid algorithm which effectively combines the iterior point method and the first-order method to achieve performance boost in large-scale linear programming. Different from the standard interior point method which relies on a costly Newton step, ABIP applies the alternating direction method of multipliers (ADMM) to approximately solve the barrier penalized problem. In this paper, we provide a new version of ABIP with several improvements. First, we develop some new implementation strategies to accelerate ABIP’s performance for linear programming. Next, we extend ABIP to solving the more general linear conic programming and establish the associated iteration complexity of the algorithm. Finally, we conduct extensive numerical experiments in both synthetic and real-world datasets to demonstrate the empirical advantage of our developments. In particular, the enhanced ABIP achieves a 5.8x reduction in the geometric mean of run time on 105 LP instances from Netlib and it compares favorably against state-of-the-art open-source solvers in a wide range of large-scale problems. Moreover, it is even comparable to the commercial solvers in some particular datasets. ...

Everyone is familiar with linear programming (LP) and its possibly NP-hard simplex algorithm. Additionally, there are interior-point methods and more. Recent advancements in the field are aimed at handling large-scale LP problems that necessitate parallel processing. One approach is the PDHG (Primal Dual Hybrid Gradient) method, a first-order optimization method for large-scale LP. Another intriguing method is the second-order ADMM. While the PDHG method is straightforward in its core concept, it employs numerous heuristic techniques, some of which have solid theoretical foundations, to expedite the optimization process. These include step size selection, adaptive restarts, primal weight updates, and more. ...

Shanghai ranks among China’s top international cities, alongside Hong Kong. Being an undergrad student in Shanghai, my friend and I represent a significant chunk of the city’s active consumer base, i.e. we contribute substantially to its vibrant atmosphere and GDP. Shanghai residents genuinely embrace international cultures, with a strong preference for North American influences. European styles, particularly those from Italy and France, also enjoy popularity. Some venture into Mexican or Latino influences, while others delve into East Asian elements like Zen culture from Japan or Korean pop culture. The Little Red Book app, similar to Instagram, serves as a platform for young people to share their “foreign lifestyle” experiences. It’s quite amusing, as some consider eating burgers and bagels as a symbol of a fancy, high-class lifestyle (ewww, seriously?). In terms of price they are symbolizing US food price indeed… Bagels, which cost around ¥8-30, barely pass as a breakfast item due to their small size, and a burger for ¥60 or more is standard (in contrast to the filling and budget-friendly 生煎包, pronounced Sheng-Jian-Bao, a type of fried meat bun, which costs about ¥15 per share). ...

Today’s blog draws inspiration from Freakonomics Radio’s podcast, which presented a three-episode series on “How to Succeed at Failing.” It’s not the most pleasant topic to discuss. In their final episode, they did something quite bold, or at least it seemed daring to me. They interviewed several individuals who had experienced failure in entrepreneurship, academia, and relationships. We often mourn, blame, and regret our own failures, but what perspective should we have when it comes to others’ failures? ...

Our former Prime Minister, Keqiang Li, has passed away in Shanghai today. Rest in peace. Li, an economist, earned his Ph.D. from Peking University and received the Sun Ye Fang Best Thesis Award for his dissertation – quite an achievement. In memory of this exceptional economist and remarkable individual, here’s a poignant tribute: 纯真而不欠闻达，善良而不失坚强，把生命高举在尘俗之上，又溶化于社会之中，这应当是我们这一代的共同追求。 Innocent yet not lacking in knowledge, kind yet unwavering in strength, lifting life above the mundane while melding with society – this should be the collective pursuit of our generation. ...

I watched and found a very interesting quote on…YouTube. Guess who said it. Trying to stop people from doing things that they want to do, doesn’t always stop them. Sounds like something Hermione Granger said The best way to get people to read something is to ban it Try reading the italicized words in staccato and you’ll get the authentic Hermione accent. OK… just kidding. Al Roth said it in his “big idea” talk on YouTube. It’s such an insight, and not only applied to market designers obviously…

I’ve been reading up on keyword query ranking optimization literature recently. In this context, we’re looking at e-commerce platforms like Amazon or Taobao, where multiple third-party sellers offer similar products when a user searches for a specific keyword. The platform’s goal is to maximize both the seller’s profit (a combination of surplus and revenue, calculated as price multiplied by quantity) and consumer satisfaction. So, the main questions here are: How should products be ranked? Is there an optimal strategy for auctioning slots to provide additional information and boost profits? However, while going through these materials, another intriguing thought crossed my mind. In the realm of consumer behavior on e-commerce platforms, inspired by recent shopping frenzies like the double-11 shopping festival, here’s an idea: could consumer search theory offer a more effective way to model the impact of placing a “buy now” button above the “add to cart” button? ...