Year	% of total labor force (national estimate)
1971	2.09
1972	2.15
1973	2
1974	1.67
1975	1.7
1976	1.9
1977	1.9
1978	4.18
1979	4.12
1980	4.01
1981	3.82
1982	3.82
1983	4.3
1984	4.16
1985	3.97
1986	3.97
1987	3.05
1988	2.16
1989	2.03
1990	1.97
1991	5.85
1992	5.18
1993	4.28
1994	4.26
1995	5.03
1996	4.79
1997	5.81
1998	5.7
1999	5.35
2000	7.16
2001	6.88
2002	7.83
2003	7.49
2004	7.4
2005	7.05
2006	0.582
2007	0.398
2008	0.423
2009	0.535
2010	0.653
2011	0.796
2012	3.667
2013	2.954
2014	1.827
2015	3.566
2016	2.286
2018	4.083
2019	4.83
2021	6.338