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.

Effective degrees of freedom corrections (updated 10/2016): edfreg.ado & edfreg.sthlp,  The updated version runs faster and allows for absorbed fixed effects, weights and noconstant. 

Working Papers

"Nearly Collinear Robust Procedures for 2SLS Estimation."  This version: September 2023.  On-line appendix.

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.

"Consistency of the OLS Bootstrap for Independently but Not-Identically Distributed Data: A Permutation Perspective."  October 2023.  On-line appendix.

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.

"Asymptotically Robust Permutation-based Randomization Confidence Intervals for Parametric OLS Regression."  This version: November 2023.  On-line appendix.

Randomization inference provides exact finite sample tests of sharp null hypotheses which fully specify the distribution of outcomes under counterfactual realizations of treatment, but the sharp null is often considered restrictive as it rules out unspecified heterogeneity in treatment response.  However, a growing literature shows that tests based upon permutations of regressors using pivotal statistics can remain asymptotically valid when the assumption regarding the permutation invariance of the data generating process used to motivate them is actually false.  For experiments where potential outcomes involve the permutation of regressors, these results show that permutation-based randomization inference, while providing exact tests of sharp nulls, can also have the same asymptotic validity as conventional tests of average treatment effects with unspecified heterogeneity and other forms of specification error in treatment response.  This paper extends this work to the consideration of interactions between treatment variables and covariates, a common feature of published regressions, as well as issues in the construction of confidence intervals and testing of subsets of treatment effects.

Published Papers by Topic

Political Economy

"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.

Applied Econometrics

"Consistency without Inference:  Instrumental Variables in Practical Application."  Forthcoming, European Economic Review. On-line appendix.

"Channelling Fisher: Randomization Tests and the Statistical Insignificance of Seemingly Significant Experimental Results."  Quarterly Journal of Economics 134 (May 2019): 557-598.  Preprint.  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. 

    Files: Appendix..  US sectoral TFP growthData and programmes.

"Inequality, the Urban-Rural Gap, and Migration." Quarterly Journal of Economics 128 (November 2013): 1727-1785. Preprint.  Appendix.  DHS based migration data.

The Aids Epidemic and African Growth

"The African Growth Miracle." Journal of Political Economy 120 (August 2012): 696-739.  Data and programmes.

"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 GenerationsQuarterly 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 People’s Republic of China during the Reform PeriodJournal of Political Economy 111 (December 2003): 1220-1261.

“The Razor’s Edge: Distortions and Incremental Reform in the People’s Republic of ChinaQuarterly 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 ExperienceQuarterly Journal of Economics 110 (August 1995): 641-680.

“Lessons from the East Asian NICs: A Contrarian ViewEuropean 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 EffectsJournal of Political Economy 106 (February 1998): 41-63.

“Substitution and Complementarity in Endogenous InnovationQuarterly Journal of Economics 108 (August 1993): 775-807.

“Invention and Bounded Learning by DoingJournal of Political Economy 101 (June 1993): 443-472.

“Learning by Doing and the Dynamic Effects of International TradeQuarterly 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.


Resting Papers

“Improved, Nearly Exact, Statistical Inference with Robust and Clustered Covariance Matrices using Effective Degrees of Freedom Corrections  January 2016.

"The Gini Coefficient for a Mixture of Ln-Normal Populations."  December 2011.  (Data and programmes).

“Demographic Fluctuations, Generational Welfare and Intergenerational Transfers.” October 2001.

“Transport, Processing and Information: Value Added and the Circuitous Movement of Goods.” May 1999.