As G.M. and Chrysler cut loose almost 2,000 dealers around the country, here is a chart that takes a longer view at the Motor City carmakers' decline:
The plot is taken from a recent report by Thomas Klier, an economist at the Chicago Fed, and shows the former Big Three's market share for passenger cars between 1955-79 and the market share for both passenger cars and light trucks (like minivans, SUVs, etc) from 1980 onward.
Detroit got its first taste of foreign competition in the mid-1950's as smaller-sized imports made inroads into the Big Three's market share. The U.S. automakers were able to fight off this initial attack on their business by introducing small cars of their own, but, as Klier points out, their commitment here was without conviction:
the Detroit automakers grew their “small” vehicles in size after having beaten back the original entry of foreign small cars...It is not surprising that the victory over imported small cars proved to be only temporary.