Template-Type: ReDIF-Article 1.0
Author-Name: Gregori Baetschmann
Author-Workplace-Name: University of Bern
Author-Email: gregori.baetschmann@soz.unibe.ch
Author-Name: Alexander Ballantyne
Author-Workplace-Name: University of Melbourne
Author-Email: ballantynea@student.unimelb.edu.au
Author-Name: Kevin E. Staub
Author-Workplace-Name: University of Melbourne
Author-Email: kevin.staub@unimelb.edu.au
Author-Person: pst600
Author-Name: Rainer Winkelmann
Author-Workplace-Name: University of Zurich
Author-Email: rainer.winkelmann@econ.uzh.ch
Author-Person: pwi6
Title: feologit: A new command for fitting fixed-effects ordered logit models
Journal: Stata Journal
Pages: 253-275
Issue: 2
Volume: 20
Year: 2020
Month: June
X-DOI: 10.1177/1536867X20930984
Abstract: In this article, we describe how to fit panel-data ordered logit mod- els with fixed effects using the new community-contributed command feologit. Fixed-effects models are increasingly popular for estimating causal effects in the social sciences because they flexibly control for unobserved time-invariant hetero- geneity. The ordered logit model is the standard model for ordered dependent variables, and this command is the first in Stata specifically for this model with fixed effects. The command includes a choice between two estimators, the blow- up and cluster (BUC) estimator introduced in Baetschmann, Staub, and Winkel- mann (2015, Journal of the Royal Statistical Society, Series A 178: 685–703) and the BUC-τ estimator in Baetschmann (2012, Economics Letters 115: 416–418). Baetschmann, Staub, and Winkelmann (2015) showed that the BUC estimator has good properties and is almost as efficient as more complex estimators such as generalized method-of-moments and empirical likelihood estimators. The com- mand and model interpretations are illustrated with an analysis of the effect of parenthood on life satisfaction using data from the German Socio-Economic Panel.
 Copyright 2020 by StataCorp LP.
Keywords:  feologit, panel data, ordered dependent variables, logistic mod- els, fixed effects, blow-up and cluster estimator
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Template-Type: ReDIF-Article 1.0
Author-Name: Javier Alejo
Author-Workplace-Name: IECON-UdelaR
Author-Email: javier.alejo@ccee.edu.uy
Author-Person: pal181
Author-Name: Antonio F. Galvao
Author-Workplace-Name: University of Arizona
Author-Email: agalvao@email.arizona.edu
Author-Name: Gabriel Montes-Rojas
Author-Workplace-Name: CONICET-IIEP-UBA
Author-Email: gabriel.montes@fce.uba.ar
Author-Person: pmo380
Title: A practical generalized propensity-score estimator for quantile continuous treatment effects
Journal: Stata Journal
Pages: 276-296
Issue: 2
Volume: 20
Year: 2020
Month: June
X-DOI: 10.1177/1536867X20930997
Abstract: In this article, we present a new command, qcte, that implements several methods for estimation and inference for quantile treatment-effects models with a continuous treatment. We propose a semiparametric two-step estimator, where the first step is based on a flexible Box–Cox model, as the default model of the command. We develop practical statistical inference procedures using boot- strap. We implement some simulations to show that the proposed methods perform well. Finally, we apply qcte to a survey of Massachusetts lottery winners to esti- mate the unconditional quantile effects of the prize amount, as a proxy of nonlabor income changes, on subsequent labor earnings from U.S. Social Security records. The empirical results reveal strong heterogeneity across unconditional quantiles.
 Copyright 2020 by StataCorp LP.
Keywords: qcte, continuous treatment, quantile treatment effects, quantile regression
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Template-Type: ReDIF-Article 1.0
Author-Name: Xavier D’Haultfoeuille
Author-Workplace-Name: CREST-ENSAE
Author-Email: xavier.dhaultfoeuille@ensae.fr
Author-Person: pdh29
Author-Name: Arnaud Maurel
Author-Workplace-Name: Duke University
Author-Email: apm16@duke.edu
Author-Person: pma1091
Author-Name: Xiaoyun Qiu
Author-Workplace-Name: Northwestern University
Author-Email: xiaoyun.qiu@u.northwestern.edu
Author-Name: Yichong Zhang
Author-Workplace-Name: Singapore Management University
Author-Email: yczhang@smu.edu.sg
Title: Estimating selection models without an instrument with Stata
Journal: Stata Journal
Pages: 297-308
Issue: 2
Volume: 20
Year: 2020
Month: June
X-DOI: 10.1177/1536867X20930998
Abstract: In this article, we present the eqregsel command, which estimates and provides bootstrap inference for sample-selection models via extremal quantile regression. eqregsel estimates a semiparametric sample-selection model without an instrument or a large support regressor and outputs the point estimates of the homogeneous linear coefficients, their bootstrap standard errors, and the p-value for a specification test.
 Copyright 2020 by StataCorp LP.
Keywords: eqregsel, sample-selection models, extremal quantile regressions
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Template-Type: ReDIF-Article 1.0
Author-Name: Marshall A. Taylor
Author-Workplace-Name: New Mexico State University
Author-Email: mtaylor2@nmsu.edu
Title: Visualization strategies for regression estimates with randomization inference
Journal: Stata Journal
Pages: 309-335
Issue: 2
Volume: 20
Year: 2020
Month: June
X-DOI: 10.1177/1536867X20930999
Abstract: Coefficient plots are a popular tool for visualizing regression estimates. The appeal of these plots is that they visualize confidence intervals around the estimates and generally center the plot around zero, meaning that any estimate that crosses zero is statistically nonsignificant at least at the alpha level around which the confidence intervals are constructed. For models with statistical sig- nificance levels determined via randomization models of inference and for which there is no standard error or confidence intervals for the estimate itself, these plots appear less useful. In this article, I illustrate a variant of the coefficient plot for regression models with p-values constructed using permutation tests. These vi- sualizations plot each estimate’s p-value and its associated confidence interval in relation to a specified alpha level. These plots can help the analyst interpret and report the statistical and substantive significances of their models. I illustrate us- ing a nonprobability sample of activists and participants at a 1962 anticommunism school.
 Copyright 2020 by StataCorp LP.
Keywords: permutation tests, visualization, coefficient plots, p-values
File-URL: http://www.stata-journal.com/article.html?article=gr0083
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Template-Type: ReDIF-Article 1.0
Author-Name: E. F. Haghish
Author-Workplace-Name: University of Göttingen
Author-Email: haghish@med.uni-goettingen.de
Title: Software documentation with markdoc 5.0
Journal: Stata Journal
Pages: 336-362
Issue: 2
Volume: 20
Year: 2020
Month: June
X-DOI:  10.1177/1536867X20931000
Abstract: markdoc is a general-purpose literate programming package for generating dynamic documents, dynamic presentation slides, Stata help files, and package vignettes in various formats. In this article, I introduce markdoc ver- sion 5.0, which performs independently of any third-party software, using the mini engine. The mini engine is a lightweight alternative to Pandoc (MacFarlane [2006, https://pandoc.org/]), completely written in Stata. I also propose a proce- dure for remodeling package documentation and data documentation in Stata and present a tutorial for generating help files, package vignettes, and GitHub Wiki documentation using markdoc.
 Copyright 2020 by StataCorp LP.
Keywords: markdoc, mini, Pandoc, statistics software, software documentation, literate programming, social coding
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Template-Type: ReDIF-Article 1.0
Author-Name: John A. Gallis
Author-Workplace-Name: Duke University
Author-Email: john.gallis@duke.edu
Author-Name: Fan Li
Author-Workplace-Name: Yale School of Public Health
Author-Email: fan.f.li@yale.edu
Author-Name: Elizabeth L. Turner
Author-Workplace-Name: Duke University
Author-Email: liz.turner@duke.edu
Title: xtgeebcv: A command for bias-corrected sandwich variance estimation for GEE analyses of cluster randomized trials
Journal: Stata Journal
Pages: 363-381
Issue: 2
Volume: 20
Year: 2020
Month: June
X-DOI: 10.1177/1536867X20931001
Abstract: Cluster randomized trials, where clusters (for example, schools or clinics) are randomized to comparison arms but measurements are taken on indi- viduals, are commonly used to evaluate interventions in public health, education, and the social sciences. Analysis is often conducted on individual-level outcomes, and such analysis methods must consider that outcomes for members of the same cluster tend to be more similar than outcomes for members of other clusters. A popular individual-level analysis technique is generalized estimating equations (GEE). However, it is common to randomize a small number of clusters (for ex- ample, 30 or fewer), and in this case, the GEE standard errors obtained from the sandwich variance estimator will be biased, leading to inflated type I errors. Some bias-corrected standard errors have been proposed and studied to account for this finite-sample bias, but none has yet been implemented in Stata. In this article, we describe several popular bias corrections to the robust sandwich variance. We then introduce our newly created command, xtgeebcv, which will allow Stata users to easily apply finite-sample corrections to standard errors obtained from GEE mod- els. We then provide examples to demonstrate the use of xtgeebcv. Finally, we discuss suggestions about which finite-sample corrections to use in which situations and consider areas of future research that may improve xtgeebcv.
 Copyright 2020 by StataCorp LP.
Keywords: xtgeebcv, cluster randomized trials, bias-corrected variances, sandwich variance, generalized estimating equations, finite-sample correction
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Template-Type: ReDIF-Article 1.0
Author-Name: Young Jun Lee
Author-Workplace-Name: University of Copenhagen
Author-Email: yjl@econ.ku.dk
Author-Name: Daniel Wilhelm
Author-Workplace-Name: University College London, CeMMAP
Author-Email: d.wilhelm@ucl.ac.uk
Author-Person: pwi343
Title: Testing for the presence of measurement error in Stata
Journal: Stata Journal
Pages: 382-404
Issue: 2
Volume: 20
Year: 2020
Month: June
X-DOI: 10.1177/1536867X20931002
Abstract: In this article, we describe how to test for the presence of measure- ment error in explanatory variables. First, we discuss the test of such hypotheses in parametric models such as linear regressions and then introduce a new com- mand, dgmtest, for a nonparametric test proposed in Wilhelm (2018, Working Paper CWP45/18, Centre for Microdata Methods and Practice, Institute for Fis- cal Studies). To illustrate the new command, we provide Monte Carlo simulations and an empirical application to testing for measurement error in administrative earnings data.
Keywords: dgmtest, nonparametric test, measurement error, measurement error bias
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Template-Type: ReDIF-Article 1.0
Author-Name: Hong Il Yoo
Author-WorkPlace-Name: Durham University Business School
Author-Email: h.i.yoo@durham.ac.uk
Author-Person: pyo103
Title: lclogit2: An enhanced command to fit latent class conditional logit models
Journal: Stata Journal
Pages: 405-425
Issue: 2
Volume: 20
Year: 2020
Month: June
X-DOI: 10.1177/1536867X20931003
Abstract: In this article, I describe the lclogit2 command, an enhanced version of lclogit (Pacifico and Yoo, 2013, Stata Journal 13: 625–639). Like its predeces- sor, lclogit2 uses the expectation-maximization algorithm to fit latent class conditional logit (LCL) models. But it executes the expectation-maximization algorithm’s core algebraic operations in Mata, so it runs considerably faster as a result. It also allows linear constraints on parameters to be imposed more conveniently and flexibly. It comes with the parallel command lclogitml2, a new stand-alone command that uses gradient-based algorithms to fit LCL models. Both lclogit2 and lclogitml2 are supported by a new postestimation command, lclogitwtp2, that evaluates willingness-to-pay measures implied by fitted LCL models.
Keywords: lclogit2, lclogitml2, lclogitpr2, lclogitcov2, lclogitwtp2, latent class model, conditional logit, expectation-maximization algorithm, lclogit, fmm, finite mixture, mixlogit, mixed logit, willingness to pay
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Template-Type: ReDIF-Article 1.0
Author-Name: Muhammad Asali
Author-WorkPlace-Name: Tbilisi State University
Author-Email: muhammad.asali@gmail.com
Author-Person: pas130
Title: vgets: A command to estimate general-to-specific VARs, Granger causality, steady-state effects, and cumulative impulse–responses
Journal: Stata Journal
Pages: 426-434
Issue: 2
Volume: 20
Year: 2020
Month: June
X-DOI: 10.1177/1536867X20931004
Abstract: Vector autoregression (VAR) estimation is a vital tool in economic studies. VARs, however, can be dimensionally cumbersome and overparameter- ized. The vgets command allows for a general-to-specific estimation of VARs— overcoming the potential overparameterization—and provides tests for Granger causality, estimates of the long-run effects, and the cumulative impulse–response of each variable in the system; it also offers diagnostics that facilitate a genuine-causality interpretation of the Granger causality tests.
Keywords: vgets, general-to-specific vector autoregressions, Granger causality, steady-state effects, cumulative impulse–responses
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Template-Type: ReDIF-Article 1.0
Author-Name: Zizhong Yan
Author-WorkPlace-Name: Jinan University
Author-Email: helloyzz@gmail.com
Author-Person: pya369
Author-Name: Wiji Arulampalam
Author-WorkPlace-Name: University of Warwick
Author-Email: wiji.arulampalam@warwick.ac.uk
Author-Person: par8
Author-Name: Valentina Corradi
Author-WorkPlace-Name: University of Surrey
Author-Email: v.corradi@surrey.ac.uk
Author-Person: pco129
Author-Name: Daniel Gutknecht
Author-WorkPlace-Name: Goethe University Frankfurt
Author-Email: daniel.gutknecht@gmx.de
Author-Person: pgu410
Title: heap: A command for fitting discrete outcome variable models in the presence of heaping at known points
Journal: Stata Journal
Pages: 435-467
Issue: 2
Volume: 20
Year: 2020
Month: June
X-DOI: 10.1177/1536867X20931005
Abstract: Self-reported survey data are often plagued by the presence of heaping. Accounting for this measurement error is crucial for the identification and consistent estimation of the underlying model (parameters) from such data. In this article, we introduce two commands. The first command, heapmph, estimates the parameters of a discrete-time mixed proportional hazard model with gamma- unobserved heterogeneity, allowing for fixed and individual-specific censoring and different-sized heap points. The second command, heapop, extends the frame- work to ordered choice outcomes, subject to heaping. We also provide suitable specification tests.
Keywords: heapmph, heapop, discrete-time duration model, mixed proportional hazards model, ordered choice model, heaping, measurement error
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Template-Type: ReDIF-Article 1.0
Author-Name: Koen Jochmans
Author-WorkPlace-Name: University of Cambridge
Author-Email: kj345@cam.ac.uk
Author-Person: pjo240
Author-Name: Vincenzo Verardi
Author-WorkPlace-Name: Université de Namur
Author-Email: vverardi@unamur.be
Author-Person: pve73
Title: Fitting exponential regression models with two-way fixed effects
Journal: Stata Journal
Pages: 468-480
Issue: 2
Volume: 20
Year: 2020
Month: June
X-DOI: 10.1177/1536867X20931006
Abstract: In this article, we introduce the commands twexp and twgravity, which implement the estimators developed in Jochmans (2017, Review of Economics and Statistics 99: 478–485) for exponential regression models with two-way fixed effects. twexp is applicable to generic n × m panel data. twgravity is written for the special case where the dataset is a cross-section on dyadic interactions between n agents. A prime example is cross-sectional bilateral trade data, where the model of interest is a gravity equation with importer and exporter effects. Both twexp and twgravity can deal with data where n and m are large, that is, where there are many fixed effects. These commands use Mata and are fast to execute.
Keywords: twexp, twgravity, exponential regression, gravity model, panel data, two-way fixed effects
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Template-Type: ReDIF-Article 1.0
Author-Name: Nicholas J. Cox
Author-WorkPlace-Name: Durham University
Author-Email: n.j.cox@durham.ac.uk
Author-Person: pco34
Title: Speaking Stata: More ways for rowwise
Journal: Stata Journal
Pages: 481-488
Issue: 2
Volume: 20
Year: 2020
Month: June
X-DOI: 10.1177/1536867X20931007
Abstract: A previous column (Cox, 2009, Stata Journal 9: 137–157) gave a review of methods for working rowwise in Stata. Here rows means observations in a dataset, and the concern is calculations in each observation with a bundle of variables. For example, a row mean variable can be generated as the mean of some numeric variables in each observation. This column is an update. It is briefly flagged that official Stata now has rowmedian() and rowpctile() functions for egen. The main focus is on returning which variable or variables are equal to the maximum or minimum in a row. The twist that requires care is that two or more variables can tie for minimum or maximum. That may entail a decision on what is to be recorded, such as all of them or just the first or last occurrence of an extreme.
Keywords: rows, functions, minimum, maximum, median, loops, egen
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Template-Type: ReDIF-Article 1.0
Author-Name: Andrew Musau
Author-WorkPlace-Name: INN University
Author-Email: andrew.musau@inn.no
Author-Person: pmu556
Title: Stata tip 136: Between-group comparisons in a scatterplot with weighted markers
Journal: Stata Journal
Pages: 489-492
Issue: 2
Volume: 20
Year: 2020
Month: June
X-DOI: 10.1177/1536867X20931008 
File-URL: http://www.stata-journal.com/article.html?article=gr0084
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Template-Type: ReDIF-Article 1.0
Author-Name: Demetris Christodoulou
Author-WorkPlace-Name: University of Sydney
Author-Email: demetris.christodoulou@sydney.edu.au
Author-Person: pch1698
Title: Stata tip 137: Interpreting constraints on slopes of rank-deficient design matrices
Journal: Stata Journal
Pages: 493-498
Issue: 2
Volume: 20
Year: 2020
Month: June
X-DOI: 10.1177/1536867X20931027
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Template-Type: ReDIF-Article 1.0
Author-Name: Nicholas J. Cox
Author-WorkPlace-Name: Durham University
Author-Email: n.j.cox@durham.ac.uk
Author-Person: pco34
Title: Stata tip 138: Local macros have local scope
Journal: Stata Journal
Pages: 499-503
Issue: 2
Volume: 20
Year: 2020
Month: June
X-DOI: 10.1177/1536867X20931028
Abstract: 
Keywords: 
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Template-Type: ReDIF-Article 1.0
Author-Name: Editors
Author-Email: editors@stata.com
Title: Software updates
Journal: Stata Journal
Pages: 504
Issue: 2
Volume: 20
Year: 2020
Month: June 
Abstract: Updates for previously published packages are provided.
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