Krugman on Interstellar Trade

While reading the comments over at Crooked Timber, I saw a link to one of our new Nobel Laureate Paul Krugman’s more insightful papers: The Theory of Interstellar Trade. The abstract reads:

This paper extends interplanetary trade theory to an interstellar setting. It is chiefly concerned with the following question: how should interest charges on goods in transit be computed when the goods travel at close to the speed of light? This is a problem because the time taken in transit will appear less to an observer travelling with the goods than to a stationary observer. A solution is derived from economic theory, and two useless but true theorems are proved.