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
Dark Matter: Measuring Unobserved Productivity Growth due to Computers through its Impact on Observables. June 2025. Online appendix.
I find systematic deviations in the relationship between measured industry total factor productivity growth and price & downstream demand growth associated with the use of computer and electronics intermediate inputs in production. The effects are robustly negative, indicating an overstatement of quality adjusted output and productivity growth in using industries of about .003 per .01 expenditure share on computer & electronic intermediates. These estimates are confirmed by regressions of measured productivity growth on own and upstream computer input use. After adjustment for mismeasurement, there is no association between computer intermediates use and total factor productivity growth.
Cointegrated Factor Augmenting Productivity Growth. June 2025. On-line appendix.
Applying tools from macroeconometrics and model selection I find strong statistical evidence of cointegration, with capital and labour productivities trading off against each other, while moving positively with intermediate input productivity. These patterns might perhaps be understood in terms of task based technical change in which the reallocation of tasks generates cost reducing tradeoffs and links between factor productivity growth rates.
"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 growth. Data 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 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
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.