Alwyn Young - Research

Working Papers

“Consistency Without Inference:  Instrumental Variables in Practical Application  June 2018.  Appendix.


I use Monte Carlo simulations, the jackknife and multiple forms of the bootstrap to study a comprehensive sample of 1359 instrumental variables regressions in 31 papers published in the journals of the American Economic Association.  Monte Carlo simulations based upon published regressions show that non-iid error processes adversely affect the size and power of IV estimates, while increasing the bias of IV relative to OLS, producing a very low ratio of power to size and mean squared error that is almost always larger than biased OLS.  Weak instrument pre-tests based upon F-statistics are found to be largely uninformative of both size and bias.  In published papers, statistically significant IV results generally depend upon only one or two observations or clusters, excluded instruments often appear to be irrelevant, there is little statistical evidence that OLS is actually substantively biased, and IV confidence intervals almost always include OLS point estimates.


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

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.

Stata code (updated 10/2016): edfreg.ado file and edfreg.sthlp, code that allows users to call for effective degrees of freedom corrections in their robust and clustered regressions.   The updated version runs faster and allows for absorbed fixed effects, weights and noconstant. 


“Channelling Fisher:  Randomization Tests and the Statistical Insignificance of Seemingly Significant Experimental Results  November 2018.  Appendix.

I follow R.A. Fisher’s The Design of Experiments (1935), using randomization statistical inference to test the null hypothesis of no treatment effects in a comprehensive sample of 53 experimental papers drawn from the journals of the American Economic Association.  In the average paper randomization tests of the significance of individual treatment effects find 13 to 22 percent fewer significant results than found using authors’ methods.  In joint tests of multiple treatment effects appearing together in tables, randomization tests yield 33 to 49 percent fewer statistically significant results than conventional tests.  Bootstrap and jackknife methods support and confirm the randomization results.

Stata code (updated 12/2018): randcmd.ado file and randcmd.sthlp, code that allows users to calculate randomization inference p-values for joint and individual tests of treatment effects in stata commands that report coefficients and standard 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. 

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

“Inequality, the Urban-Rural Gap, and MigrationQuarterly Journal of Economics 128 (November 2013): 1727-1785.  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

"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.