Differences in real interest rates across developed economies are puzzlingly large and persistent. I propose a simple explanation: bonds issued in the currencies of larger economies are expensive because they insure against shocks that affect a larger fraction of the world economy. I show that, indeed, differences in the size of economies explain a large fraction of the cross‐sectional variation in currency returns. The data also support additional implications of the model: the introduction of a currency union lowers interest rates in participating countries, and stocks in the nontraded sector of larger economies pay lower expected returns.

We use the fall of the Berlin Wall in 1989 to show that personal relationships which individuals maintain for noneconomic reasons can be an important determinant of regional economic growth. We show that West German households who had social ties to East Germany in 1989 experienced a persistent rise in their personal incomes after the fall of the Berlin Wall. Moreover, the presence of these households significantly affects economic performance at the regional level: it increases the returns to entrepreneurial activity, the share of households who become entrepreneurs, and the likelihood that firms based within a given West German region invest in East Germany. As a result, West German regions that (for idiosyncratic reasons) have a high concentration of households with social ties to the East exhibit substantially higher growth in income per capita in the early 1990s. A one standard deviation rise in the share of households with social ties to East Germany in 1989 is associated with a 4.7 percentage point rise in income per capita over six years. We interpret our findings as evidence of a causal link between social ties and regional economic development.