Year	% of total labor force (national estimate)
1991	2.5742041864253338
1992	2.548507095689844
1993	2.794312145600728
1994	3.1176646043155953
1995	3.057355506421882
1996	3.2252633511177446
1997	3.3205886915657246
1998	3.5442526826966176
1999	3.5969113509844437
2000	4.069035355309498
2001	3.783492511678152
2002	4.205109659443135
2003	4.308367638186876
2004	4.330851888869676
2005	4.466975599836675
2006	4.370206281596101
2007	4.2013085074871155
2008	4.3774878307187
2009	4.225339892218144
2010	3.9376540397393156
2011	3.8779633848575306
2012	3.802499173429912
2013	3.744037974931853
2014	3.7588747559493743
2017	3.531863472845632
2018	4.298313333933301
2019	4.33959802752366
2020	4.826766663695262
2021	4.551939945434292