The effect of a program or treatment may vary according to observed characteristics. In such a setting, it may not only be of interest to determine whether the program or treatment has an effect on some sub-population defined by these observed characteristics, but also to determine for which...

The large literature on costly signaling and the somewhat scant literature on preference signaling had varying success in showing the effectiveness of signals. We use a field experiment to show that even when everyone can send a signal, signals are free and the only costs are opportunity costs,...

This paper examines non-price competition among colleges to attract highly qualified students, exploiting the South Korean setting where the national government sets rules governing applications. We identify some basic facts about the behavior of colleges before and after a 1994 policy change...

We estimate the causal impact of school and classroom gender composition on achievement. We take advantage of the random assignment of Korean middle school students to single-sex schools, co-educational (coed) schools with single-sex classes, and coed schools with mixed-gender classes. Male...