In their study, titled “Congress and the Stock Market,” they found that the Dow Jones Industrial Average from 1897 through 2004 produced the equivalent of a 13.8% annualized return when Congress was not in session, versus 2% when Congress was in session. They found a similar result for the period beginning in 1957, when the S&P 500 was created.

A session defined by Republican wins concluded with a Republican rebellion this week in the House of Representatives.