Year	% of total labor force (national estimate)
1972	3.06
1973	2.78
1976	1.92
1977	2.32
1978	2.36
1979	2.76
1981	3.99
1982	4.83
1983	4.62
1984	4.04
1985	3.38
1986	2.37
1987	3.56
1988	3.79
1989	4.145
1990	4.703
1992	7.086
1993	6.03
1995	7.092
1996	8.035
1997	9.003
1998	10.15
1999	11.125
2001	10.649
2002	10.641
2003	11.169
2004	10.072
2005	10.551
2006	9.692
2007	9.28
2008	8.268
2009	9.419
2011	7.578
2012	7.251
2013	7.071
2014	6.755
2015	8.538
2016	11.58
2017	12.792
2018	12.33
2019	11.936
2020	13.697
2021	13.159
2022	9.231
2023	7.947