Yichen (Joshua) Shen's Lab
研究室紹介Laboratory
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Overview of the Lab
My research focuses on providing empirical evidence on a various of economic topics through causal inference technique, or evidence-based policy analyses. Some of policies included but not limited to health insurance, pandemic, compulsory schooling laws, and minimum wages in the fields of health economic, education economic, economic of crime, labor economic, and other fields of economic.
1. Health Economics
A big part of health economic policy analyses is related to health insurance. In particular, the focus is on the expansion of health insurance, such as the Afford Care Act in the United States in 2010 and universal health insurance in Japan in 1961. Much of the research examines the impact of these policies on health, or mortality outcome, and health behavior. Similar to these studies, I recently worked on the impact of the 1995's universal health insurance in Taiwan affect health behaviors, such as alcohol use and smoking. To investigate how the insurance implemented in 1995 affect behaviors in Taiwan, a causal inference technique, or a difference-in-differences approach was used.
That is, I compared the health behaviors of individiduals who were exposed to the policy, or those who do not have any health insurance before 1995 (treatment group), and the health behaviors of individuals who were not exposed to the policy, or those who had some sort of health insurance before 1995 (control group) as the left figure shown.
After the regression analyses, one can observe that universal health insurance improved the health behaviors of treatment group. For example, I plotted the smoking prevalence between treatment and control groups between 1989 to 2003. We can see that those in the treatment group (red line) had a significant decline in smoking compared to those in the control group (blue line) after 1995, the year that universal health insurance implemented. In sum, this showed that universal health insurance led to better health behaviors.
2. Education Economics
Education economic revolves around understanding the impact of how education could affect a variety of outcomes, such as mortality and employment. For example, does junior high education improve mortality rates in Japan using the compulsory schooling laws in 1947? Masuda and Shigeoka (2024) showed that there were little to no effect of education on later-life mortality rates in Japan. Similarly, I examined the effect of college education on health behaviors in Japan using a distortion from Japanese superstition.
The superistion that I am referring to is Firehorse Year, or Hinoeuma. The Firehorse Year occured every 60 years with the most recent happening in 1966. Japanese believe that women born under this sign are particularly dominating and headstrong in terms of their personalities. Thus, shortening husbands' lives due to stresses. As a result, the fertility rates in 1966 significantly decline due to the belief of this superistion as shown in the left figure.
Because of the decline in the fertlity in 1966, we can observe that there were fewer people born and competing for education resources. That is, we can observe that college education significantly increase for those born in 1966, or attending college in 1985/1986 as the panel (b) of the left figure shown. The effect is only limited to college due to the competitiveness of college education in Japan.
Using the change in college education from the Firehorse year, we identified the effect of college education on health behaviors in Japan. Without going into too much detail on method, we can see that college education led to better health behaviors in Japan on average. Specfically, we can observe that one additional year of college decreased smoking and drinking and increased cancer screening use in Japan! This does implied that college education has a beneficial impact on health behaviors among Japanese.
Reference:
Masuda, K., & Shigeoka, H. (2023). Education and later-life mortality: Evidence from a school reform in Japan (No. w31472). National Bureau of Economic Research.
3. Labor Economics (and Economic of Crime)
Labor economics evaulate how different labor policies could affect employment, productivity, and other labor-related outcomes. There are many topics in this field, so I will be focusing on the research that are most relevant to mine own: minimum wages. In particular, recently my work evaulates the impact of the 2007's minimum wage reform on crime in Japan. It is the intersection of two fields: labor economics and economics of crime.
In 2007, Japanese government implemented a policy to increase the minimum wages across prefectures. Specifically, some prefectures' minimum wages were raised significantly since the reform. These prefectures were Hokkaido, Aomori, Miyagi, Akita, Saitama, Chiba, Tokyo, Kanagawa, Kyoto, Osaka, Hyogo, and Hiroshima. Using these prefectures as treatment group, we can compare the crime activitites between these two groups across years between 2002 to 2014. Observing the left figure, we can see that the trends of violent crime do not change after 2007 for the treatment group compared to the control group. Instead, we observe that property crime actually diverged and decreased after 2007 between the treatment and control groups. This suggested that the 2007's minimum wage reform in Japan may have unintentionally lower the property crime in the prefectures with an increase in minimum wages.
Message for Prospective and/or Current Students and Supervisee
For current students, please pay attention to your mental and physical health during your stay in the school. It is difficult to joggle both work and study at the same time. Do leave some time to relax and rest.
For potential supervisee, it would be a good idea to read through some books or new articles to understand how policy reform work. Also, read economic journal article(s) as it would help build your knowledge regarding your research. If you want to read something interest in Economics to help movitate you, try to listen and/or read Freaknomics. Also, please do not hesitate to contact me through email.