Alwyn Young - Research
Stata Code (all programmes also available through ssc install in Stata)
Collinearity robust 2SLS estimates: pariv.ado & pariv.sthlp. 2SLS estimates that are computationally more accurate when regressors are nearly collinear. In such circumstances, the point estimates produced by Stata are sensitive to reorderings of the data or variables.
Randomization confidence intervals for OLS regression models: randcmdci.ado & randcmdci.sthlp. Randomization-t confidence intervals and p-values that are asymptotically robust to deviations from the sharp null in favour of average treatment effects.
Randomization inference p-values (updated 5/2020): randcmd.ado & randcmd.sthlp. Randomization-c and -t p-values for individual treatment effects and joint Wald and Westfall-Young multiple-testing tests of statistical significance for equations with multiple treatment effects and for an experiment as a whole. The omnibus test (available in earlier versions) has been restored at the request of users.
Stata's two-stage least squares (2SLS) computation procedures are sensitive to near collinearity among regressors, allowing situations in which reported results depend upon factors as irrelevant as the order of the data and variables. This note illustrates this claim with the public use data of Oreopoulos (AER 2006), where by permuting the order of the variables the instrumented coefficient estimate can be made to vary between .012 and 30.0 in a single specification, reviews different methods for improving the accuracy of 2SLS estimates, and provides an ado file for collinearity robust 2SLS estimation in Stata.
Analyzing the distribution of the pairs and wild OLS bootstrap as that of a permutation statistic reveals moment conditions sufficient for consistency conditional on independently but not-necessarily identically distributed (inid) data which cover more general regression models than earlier inid results and are by and large less demanding than previous results for independently and identically distributed data.
Merging results concerning the asymptotic distribution of permutation statistics with White's (1980) proof of the asymptotic accuracy of heteroskedasticity robust inference, this paper shows that insofar as conventional inference asymptotically provides accurate coverage probabilities, randomization tests using sharp nulls that incorrectly specify an absence of heterogeneity do so as well, regardless of covariate interactions or the level of standard error clustering. Intuitively, in all cases the distribution of the Wald statistic across permutations of treatment converges to that of a chi-squared variable. When the conventional test statistic is similarly asymptotically distributed chi-squared, the order statistics of the permutation distribution average the linearly accurate coverage probabilities of the conventional test. The additional to White (1980) assumptions used to prove the result are that treatment is iid, interactions are included separately as covariates, sufficiently high moments of treatment, interactions and errors exist, and the maximum size of interdependent observations is bounded.
Published Papers by Topic
"Misspecified Politics and the Recurrence of Populism." (joint with Gilat Levy and Ronny Razin). American Economic Review 112 (March 2022): 928-962. On-line appendix.
"Consistency without Inference: Instrumental Variables in Practical Application." Forthcoming, European Economic Review. On-line appendix.
Macroeconomic Implications of Worker Self Selection
"Structural Transformation, the Mismeasurement of Productivity Growth, and the Cost Disease of Services." American Economic Review 104 (November 2014): 3635-67.
The Aids Epidemic and African Growth
"In Sorrow to Bring Forth Children: Fertility amidst the Plague of HIV." Journal of Economic Growth 12 (December 2007): 283-327.
The Gift of the Dying: The Tragedy of AIDS and the Welfare of Future African Generations. Quarterly Journal of Economics 120 (May 2005): 423-466.
Growth and Reform in
the People's Republic of
Gold into Base Metals: Productivity Growth in the Peoples Republic of China during the Reform Period. Journal of Political Economy 111 (December 2003): 1220-1261.
The Razors Edge: Distortions and Incremental Reform in the
Peoples Republic of
East Asian Productivity Growth
The Tyranny of Numbers: Confronting the Statistical Realities of the East Asian Growth Experience. Quarterly Journal of Economics 110 (August 1995): 641-680.
Lessons from the East Asian NICs: A Contrarian View. European Economic Review 38 (1994): 964-973.
A Tale of Two Cities: Factor
Accumulation and Technical Change in Hong Kong and Singapore. In
NBER, Macroeconomics Annual 1992.
Models of Endogenous Growth
Growth without Scale Effects. Journal of Political Economy 106 (February 1998): 41-63.
Substitution and Complementarity in Endogenous Innovation. Quarterly Journal of Economics 108 (August 1993): 775-807.
Invention and Bounded Learning by Doing. Journal of Political Economy 101 (June 1993): 443-472.
Learning by Doing and the Dynamic Effects of International Trade. Quarterly Journal of Economics 106 (May 1991): 369-405.
Ballistic Missile Defense
Ballistic Missile Defense: Capabilities and Constraints. The Fletcher Forum
8 (Winter 1984). Reprinted in
Department of Defense, Current News,
Special Edition, No. 1142, 25 April 1984 and
"The Gini Coefficient for a Mixture of Ln-Normal Populations." December 2011. (Data and programmes).