When Alaska Sen. Ted Stevens was convicted in October on seven counts of failing to properly report gifts and services he received in connection with a home renovation, it was merely the latest iteration of a very old story. The attempt to influence politicians, whether by out-and-out bribes or more subtle means, is as old as politics itself.

American history is rife with corruption sagas, from Teapot Dome to Abscam to Rep. Randall “Duke” Cunningham’s 2006 guilty plea to taking at least $2.6 million in bribes. The persistence of such behavior is a testament to simple economics.