Year	% of total labor force (national estimate)
1970	2.42
1971	2.67
1972	2.77
1973	2.69
1974	2.86
1975	4.08
1976	4.47
1977	5.01
1978	5.27
1979	6.03
1980	6.42
1981	7.54
1982	8.2
1983	7.918
1984	9.533
1985	10.259
1986	10.23
1987	10.735
1988	10.18
1989	9.618
1990	9.36
1991	9.134
1992	10.203
1993	11.321
1994	12.593
1995	11.834
1996	12.367
1997	12.566
1998	12.074
1999	11.981
2000	10.218
2001	8.61
2002	8.702
2003	8.307
2004	8.914
2005	8.882
2006	8.833
2007	8.009
2008	7.386
2009	9.122
2010	9.279
2011	9.228
2012	9.841
2013	9.913
2014	10.273
2015	10.354
2016	10.057
2017	9.41
2018	9.018
2019	8.415
2020	8.01
2021	7.874
2022	7.308
2023	7.335