Year	% of total labor force (national estimate)
1972	1.67
1973	1.55
1974	1.48
1975	2.29
1976	1.76
1977	1.46
1978	1.8
1979	1.99
1980	1.65
1981	2.03
1982	1.7
1983	2.04
1984	2.9
1985	2.32
1986	1.79
1987	2.03
1988	3.02
1989	4.83
1990	5.261
1991	5.407
1992	5.91
1993	5.965
1994	5.349
1995	6.307
1996	5.036
1997	4.687
1998	3.737
1999	3.247
2000	3.458
2001	3.738
2002	4.022
2003	4.221
2004	4.256
2005	4.381
2006	3.397
2007	2.493
2008	2.521
2009	3.1
2010	3.527
2011	3.196
2012	3.129
2013	3.425
2014	3.486
2015	4.296
2016	4.68
2017	4.164
2018	3.801
2019	3.684
2020	4.424
2021	4.359
2022	3.231
2023	3.573