Please use this identifier to cite or link to this item: https://hdl.handle.net/10419/314600 
Year of Publication: 
2025
Series/Report no.: 
IZA Discussion Papers No. 17703
Publisher: 
Institute of Labor Economics (IZA), Bonn
Abstract: 
We estimate the causal effect of exposure to math during high school on university major choice and performance, using a unique administrative dataset of 1,396 twins extracted from the entire student population enrolled between 2011 and 2021 at an Italian university. We apply a Twin Fixed Effect (TFE) estimator to account for unobserved factors like shared family background. We find that attending a low-math high school reduces the likelihood of enrolling in STEM majors by 32.6 percentage points and improves university performance, by increasing the likelihood of on-time graduation by 11.7 percentage points and boosting grades by 0.139 standard deviations. Leveraging a high school reform that expanded the math content in traditionally low-math curricula, we show that the added math background further reduces STEM enrollment for treated students, while it drives their improvement in performance. Our results suggest that, while increased math exposure does not necessarily boost STEM enrollment, it equips students with skills that help them improve their university outcomes. Compared with TFE, Ordinary Least Squares estimates of the effect of math exhibit a downward bias. The same applies to Difference-in-Differences estimates of the effect of the reform obtained using the entire student population.
Subjects: 
math exposure
twins
twin fixed effects
major choice
stem
university performance
high school reform
JEL: 
D10
I21
I23
I28
J24
Document Type: 
Working Paper

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