Year	% of total labor force (national estimate)
1991	2.6126554872356844
1992	2.6117054459484565
1993	2.865197458232852
1994	3.15579827788888
1995	3.105462071342571
1996	3.2654353547986723
1997	3.356000591783571
1998	3.702082386252382
1999	3.7737332072614467
2000	4.139267773784098
2001	3.894842147016334
2002	4.295231125094234
2003	4.375717019204329
2004	4.356566168660087
2005	4.453684256052426
2006	4.337984511888985
2007	4.157077679750002
2008	4.316220301505718
2009	4.28099759993013
2010	4.010644670146366
2011	3.9125627639122222
2012	3.8303981719372513
2013	3.7611601109010198
2014	3.761106023731025
2017	3.5221102436983687
2018	4.190384965587933
2019	4.214153014522622
2020	4.7101329205404046
2021	4.438431396901467