This article investigates the wage differentials of similar occupations ill
three for hire transportation carrier industries, railroad truck, and moto
r bus, under regulation and deregulation. The estimation results indicate t
hat the onion wage gaps among all occupations have widened under deregulati
on. Specifically, the union wages of railroad occupations have increased re
lative to those of truck drivers and the union wages of truck drivers have
increased relative to those of motor bus drivers. Further; wage gaps for al
l occupations for this period are greater among nounion than among union wo
rkers.