Alwyn Young - Research

Stata Code

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.

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 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

"Consistency of the OLS Bootstrap for Independently but Not-Identically Distributed Data: A Permutation Perspective." May 2021. On-line appendix.

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.

"Asymptotically Robust Randomization Confidence Intervals for Parametric OLS Regression." September 2020. On-line appendix.

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 use

__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.

Published Papers by Topic

**Applied Econometrics**

"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 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.

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.