jerryasher recommends Paul Krugman's blog at the NYTimes, where he introduces a paper he wrote, The Theory of Interstellar Trade, with tongue very much in cheek. Some packrat academician was kind enough to send him a scan, because "back then academics did their work with typewriters, abacuses, and stone axes." Abstract: This paper extends interplanetary trade theory to an interstellar setting. It is chiefly concerned with the following question: how should interest rates 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 traveling with the goods than to a stationary observer. A solution is derived from economic theory, and two useless but true theorems are proved... This paper, then, is a serious analysis of a ridiculous subject, which is of course the opposite of what is usual in economics."