Year	% of total labor force (national estimate)
1974	9.6
1975	8.21
1976	8.79
1980	9.9
1981	8.7
1982	9.6
1983	9.25
1986	6.28
1988	4.27
1989	2.81
1990	2.831
1991	3.509
1992	3.837
1993	5.527
1994	7.6
1995	7.9
1996	8.283
1997	9.67
1998	7.74
1999	13.95
2000	15.32
2001	13.213
2002	11.39
2004	7.7
2005	7
2006	7.4
2007	8.3
2009	9.3
2010	8.2
2011	13.3
2012	12.2
2013	11.5
2014	7.6
2015	6.9
2016	5.4