Nice graph showing the declining US manufacturers ("The Big 3") share of the car/truck market. I am looking for help to explain the 1980's and half of the 90's.

The first graph (from Carpe Diem) shows the change in market share for the US auto market between "The Big Three" and foreign producers from 1961 to 2012.  From start to finish, the steady decline in US share and the rise of the foreign share is quite dramatic.  The US producer share of vehicles produced went from over 80% to about 44%. Almost half as much.

However, upon closer inspection I noticed 3 distinct segments that were not prominent before I doctored the graph (apologies to Dr Perry).  I put directional arrows to show these segments. Don't confuse these arrows with mathematically correct trend-lines---I just eye-balled them.

I found the center segment to be a curious one.  From 1981 to 1996 the respective market shares stayed remarkably constant. On either side of this 16 year segment US share decreased significantly, more so post-1996.

Why the pause?  I am too lazy tonight to Google it.  Any educated/informed guesses?