Year	% of total labor force (national estimate)
1969	4.3
1970	6.4
1971	7.5
1972	4.7
1973	4.5
1974	5.1
1975	4.81
1976	6.2
1977	5
1978	4.5
1979	3.8
1983	4.24
1984	4.7
1989	5.78
1991	6.75
1993	7.4
1994	7.5
1995	7.2
1999	7.6
2001	11.63
2002	11.68
2003	10.28
2006	8.17
2007	8.42
2008	10.94
2009	8.14
2010	8.61