The greatest assault on American middle-class prosperity is the relentless, four-decade-long inflation in higher education — In 1980 a gallon of gasoline cost $1.19. Today it’s $3.41, a 2.7% annual increase. But undergraduate tuition has risen nearly three times as fast: 6.7% a year at public colleges, for an increase of nearly 1,400%. The greatest assault on middle-class America’s prosperity may be the relentless, four-decade-long inflation…