Year	% of total labor force (national estimate)
1980	5.6
1981	5.1
1982	3.6
1983	4.4
1984	5.7
1985	6.7
1986	6.4
1987	6.1
1988	7
1989	7.3
1990	9.5
1991	9.1
1992	26.5
1993	22.3
1994	18.4
1995	12.9
1996	12.3
1997	14.9
1998	17.7
1999	18.4
2000	16.8
2001	16.4
2002	4.615
2003	15
2004	14.4
2005	6.566
2006	13.8
2007	15.966
2008	13.06
2009	13.674
2010	14.086
2011	13.481
2012	13.376
2013	15.866
2014	18.055
2015	17.193
2016	15.418
2017	13.616
2018	12.304
2019	11.466