Easy demand-system estimation with quaids

Previously, to fit an almost-ideal demand system in Stata, one would have to use the nlsur command and write a function evaluator program as described in [R] nlsur and Poi (2008, Stata Journal 8: 554–556). In this article, I introduce the command quaids, which obviates the need for any programming by the user. The command fits Deaton and Muellbauer's (1980b, American Economic Review 70: 312–326) original almost-ideal demand-system model as well as Banks, Blundell, and Lewbel's (1997, Review of Economics and Statistics 79: 527–539) quadratic variant. Demographic variables can also be included in the model. Postestimation tools calculate expenditure and price elasticities.