Drunken driving incidents have fallen 30 percent in the last five years, and last year were at their lowest mark in nearly two decades, according to a new federal report. The decline may be due to the down economy: Other research suggests people are still drinking as heavily as in years past, so some may just be finding cheaper ways of imbibing than by going to bars, night clubs and restaurants."One possibility is that people are drinking at home more and driving less after drinking," said Dr.