Alwyn Young - Research
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 (also available through ssc install in Stata). 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.
Nearly Collinear Regressors and the Replicability and Robustness of Published Results (comment on Oreopoulos 2006). July 2021.
Users of the Oreopoulos (2006) public
use code and data have had trouble replicating the paper's estimated Mincerian
return to schooling for the
Analyzing the distribution of the OLS bootstrap as that of a permutation statistic easily reveals moment conditions sufficient for consistency with full-sampling and independently but potentially not-identically distributed (inid) data which are less demanding than previous results for independently and identically distributed (iid) data. With inid data sub-sampling, which often solves failures of the bootstrap and in the case of iid data delivers consistency with minimal assumptions, may render the OLS bootstrap inconsistent in environments where full-sampling is otherwise consistent. Intuitively, sub-sampling increases the tail influence of increasingly extreme but increasingly rare distributions, whose effects are otherwise averaged out in the full sample.
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.
"Misspecified Politics and the Recurrence of Populism." (joint with Gilat Levy and Ronny Razin). Forthcoming American Economic Review. On-line appendix.
We develop a dynamic model of political competition between two groups that differ in their subjective model of the data generating process for a common outcome. One group has a simpler model than the other group as they ignore some relevant policy variables. We show that policy cycles must arise and that simple world views - which can be interpreted as populist world views - imply extreme policy choices. Periods in which those with a more complex model govern increase the specification error of the simpler world view, leading the latter to overestimate the positive impact of a few extreme policy actions.
Leverage, Heteroskedasticity and Instrumental Variables in Practical Application. (formerly "Consistency without Inference") June 2021. Appendix.
I propose bias and effective degrees of freedom corrections, based upon mimicking the first two moment properties of a chi-squared variable, to statistical inference using robust and clustered covariance matrices. Simulation, using 1378 practical regression examples found in 44 experimental papers, shows that these corrections render the test statistics nearly exact in the face of ideal iid normal errors and provide large improvements in the accuracy of statistical inference in the presence of distinctly non-iid non-normal errors.
Published Papers by Topic
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 China
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 China. Quarterly Journal of Economics 115 (November 2000): 1091-1135.
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. Cambridge, MA: MIT Press, 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 Air War College, Strategic Nuclear Force Posture, Vol. II, Chap. 5, December 1984.
"The Gini Coefficient for a Mixture of Ln-Normal Populations." December 2011. (Data and programmes).