https://www.msu.edu/~kwakdo/
Kwak, D. (2010). Implementation of instrumental variable quantile regression (IVQR) methods. [pdf]
(Abstract) A new Stata command, ivqreg, is introduced to perform a quantile regression for estimating treatment effect using the robust standard error formula in Chernozhukov and Hansen (2006) for an exactly-identified instrumental variable case and the formula in Chernozhukov and Hansen (2008) for an over-identified instrumental variable case. We examine finite sample properties of the instrumental variable quantile regression (IVQR) estimator for convergence and coverage using Monte Carlo simulations. We demonstrate the uses of ivqreg command on data on educational achievement and earnings.
Kwak, D. (2010). Inverse probability weighted estimation for the effect of kindergarten enrollment age and peer quality on student academic achievement for grades K-12.
(Abstract) Using Tennessee's Project STAR experiment data and focusing on kindergarten entering students aged 5, we estimate the effect of kinder entering age on academic achievement for grades K-12. We estimate the age effect on achievement by inverse probability weighted (IPW) estimator since STAR sample has substantial missing data by attrition such that only 2,813 students out of 5,440 students remain in the program by the end of program. We find that age has positive effect until first grade and no statistically significant effect for second and third graders. However, age has statistically significant negative effect afterward. Furthermore, we also estimate the long-run effect of peer quality on academic achievement for grades K-12. Random assignments of students and teachers in the Project STAR experiment guarantee that the peer quality effect to be exogenous once we successfully control for missing data. Peer quality measures are constructed using the class average scores of cognitive and non-cognitive skill tests for grades in K-3. IPW estimates provide evidence that peer quality in K-3 has an long-term positive effect on student academic achievement. The positive effect of peer quality persists throughout all grades including high school grade.