The growth in high- and low-skill jobs, coupled with little growth in the middle-skill groups, has changed the composition of the workforce. The leftmost bars in Chart 3 show the share of U.S. workers in each skill category in 1980 and 2010. While both high-skill and low-skill job shares increased, the lower-middle skill group’s job share shrank. In 1980, nearly half of all workers were employed in lower-middle-skill occupations. Among the occupations in this group, machine operators accounted for 10 percent of the U.S. workforce and administrative support workers accounted for 18 percent.