Year	% of total labor force (national estimate)
1975	0.3
1976	0.7
1977	0.4
1978	0.4
1979	0.4
1980	0.2
1981	0.2
1982	0.4
1983	0.9
1984	1.1
1985	1
1986	0.8
1987	0.8
1988	0.7
1989	0.6
1990	2.07
1991	1.818
1992	2.344
1993	3.551
1994	3.58
1995	3.094
1996	3.684
1997	4.127
1998	3.568
1999	3.053
2000	2.658
2001	2.49
2002	2.924
2003	4.117
2004	4.316
2005	4.437
2006	3.995
2007	3.641
2008	3.35
2009	4.109
2010	4.808
2011	4.409
2012	4.491
2013	4.747
2014	4.826
2015	4.801
2016	4.918
2017	4.797
2018	4.713
2019	4.394
2020	4.817
2021	5.097
2022	4.3
2023	4.05