Before we get further, let me address some misunderstandings around my discussion of instrumental variables research in my previous post.

FORBES: Seeking Common Ground on Medicaid

Using desired fertility constructed from both retrospective and prospective questions, together with instrumental variables estimation, it is shown this strong result is not affected by either ex-post rationalization of births nor the dependence of desired fertility on contraceptive access or cost.

FORBES: UN Population Predictions: Up To 15 Billion by 2100