If you’re a United States senator thinking about retiring before the November 2016 elections, the clock is ticking.
Since 1991, more than 80 percent of senators who have announced their retirements already did so by January of their election years. From 1920 through 1990, just 46 percent of retiring senators did the same, according to a new paper by David Karol, a professor of government and politics at the University of Maryland.