Stata 16 Feature highlights：
1. Lasso
2. Reporting
3. Meta-analysis
4. Choice models
5. Python integration
6. New in Bayesian analysis—Multiple chains, predictions, and more
7. Panel-data ERMs
8. Import data from SAS and SPSS
9. Nonparametric series regression
10. Multiple datasets in memory
11. Sample-size analysis for confidence intervals
12. Nonlinear DSGE models
13. Multiple-group IRT models
14. xtheckman
15. Multiple-dose pharmacokinetic modeling
16. Heteroskedastic ordered probit models
17. Graph sizes in printer points, centimeters, and inches
18. Numerical integration
19. Linear programming
20. Stata in Korean
21. Mac interface now supports Dark Mode and native tabbed windows
22. Do-file Editor—Autocompletion and more syntax highlighting
Multiple-group IRT models in Stata
IRT models explore the relationship between a latent (unobserved) trait and items that measure aspects of the trait. This often arises in standardized testing where the trait of interest is ability, such as mathematical ability. A set of items (test questions) is designed, and the responses measure this unobserved trait. Researchers in education, psychology, and health frequently fit IRT models.
Stata’s irt commands fit 1-, 2-, and 3-parameter logistic models. They also fit graded response, nominal response, partial credit, and rating scale models, and any combination of them. And after fitting a model, irtgraph graphs item-characteristic curves, test characteristic curves, item information functions, and test information functions.
New in Stata 16, the irt commands allow comparisons across groups. Take any of the existing irt commands, add a group(varname) option, and fit the corresponding multiple-group model. For instance, type
. irt 2pl item1-item10, group(female)
and fit a two-group 2PL model.
Group-specific means and variances of the latent trait will be estimated. Group-specific difficulty and discrimination parameters can also be estimated for one or more items. With constraints, you can specify exactly which parameters are allowed to vary and which parameters are constrained to be equal across groups.
You can even use likelihood-ratio tests to compare models with and without constraints to perform an IRT model-based test of differential item functioning.
Nonlinear DSGE models in Stata 15
In Stata 15, we introduced the dsge command for fitting linear DSGE models, which are time-series models used in economics and finance. These models are an alternative to traditional forecasting models. Both attempt to explain aggregate economic phenomena, but DSGE models do this on the basis of models derived from microeconomic theory.
New in Stata 16, the dsgenl command fits nonlinear DSGE models. Most DSGE models are nonlinear, and this means that you no longer need to linearize them by hand. When you enter equations into dsgenl, it linearizes them for you.
After estimating the parameters of your model with dsgenl, you can obtain the transition and policy matrices; determine the model’s steady state; estimate variables’ variances, covariances, and autocovariances implied by the system of equations; and create and graph impulse–response functions.
This is likely to be the favorite feature of macroeconomists and anyone working in a central bank.
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