Year	% of total labor force (national estimate)
1974	1.77
1975	4.5
1976	6.4
1978	7.89
1979	7.94
1983	7.3
1985	8.18
1986	8.698
1987	7.377
1988	6.008
1989	5.13
1990	4.645
1991	3.919
1992	3.985
1993	5.301
1994	6.709
1995	7.064
1996	7.298
1997	6.571
1998	4.64
1999	4.579
2000	3.806
2001	3.829
2002	4.497
2003	6.132
2004	6.319
2005	7.582
2006	7.649
2007	7.966
2008	7.553
2009	9.432
2010	10.771
2011	12.682
2012	15.531
2013	16.188
2014	13.897
2015	12.447
2016	11.068
2017	8.869
2018	6.994
2019	6.464
2020	6.801
2021	6.577
2022	6.011
2023	6.509