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Towards a more systematic approach to external validity: understanding site-selection bias

Jed Friedman's picture
The impact evaluation of a new policy or program aims to inform the decision on wider adoption and even, perhaps, national scale-up. Yet often the practice of IE involves a study in one localized area – a sample “site” in the terminology of a newly revised working paper by Hunt Allcott. This working paper leverages a unique program roll-out in the U.S. to explore the challenges and pitfalls that arise when generalizing IE results from a handful of sites to a larger context. And the leap from applying impact estimates taken in one site to the larger world is not always straightforward

Generating Regression and Summary Statistics Tables in Stata: A checklist and code

Matthew Groh's picture
As a research assistant working for David, I’ve had to create many, many regression and summary statistics tables. Just the other day, I sent David a draft of some tables for a paper that we are working on. After re-reading the draft, I realized that I had forgotten to label dependent variables and add joint significance tests in a couple regression tables. In an attempt to avoid forgetting these details in the future and potentially help future researchers, I thought I’d post a checklist for generating regression and summary statistics tables.

How stable are time preferences? Mixed evidence from two new studies

David McKenzie's picture
The discount rate used by individuals to trade off utility in the future against utility today is a fundamental parameter of decision theory. It is typically elicited in surveys by asking individuals to make choices between receiving an amount today, and a different amount at some point in the future. There are lots of key design issues involved in doing this (e.g.

Growth, Top Incomes, and Social Welfare

Aart Kraay's picture
Trends in income inequality are at the center of development policy discussions these days.  Part of this renewed attention is no doubt a tribute to Thomas Piketty’s pioneering work to measure top income shares using income tax data, as well as his much-discussed new book.  Piketty’s work shows some dramatic trends in inequality at the top end of the income distribution.  For example, in countries such as C