This paper presents an overlapping generations model to explain why humans live in families rather than in other pair groupings. Since most non-human species are not familial, something special must be behind the family. It is shown that the two necessary features that explain the origin of the...

This paper provides a general formulation of the regression discontinuity (RD) design and applies this method to analyse the effects of the 1995 UK pill scare. We show that in the five months following a health warning on the "third generation" pill, conception rates rose by more than 7%,...