Year % of total labor force 1991 31.993715409230717 1992 32.160086500249605 1993 32.283994258414204 1994 32.40648562367421 1995 32.56823358873473 1996 32.70588715770558 1997 32.84746532937346 1998 32.98586498769962 1999 33.1190409944314 2000 33.25398289370213 2001 31.887826295453387 2002 32.89995325727541 2003 34.40298398088845 2004 34.20784841655573 2005 35.18363901606555 2006 35.568792359546464 2007 35.21199472759227 2008 35.980035312676385 2009 36.32320197440781 2010 37.19862629047693 2011 36.955469208030436 2012 37.153305594885474 2013 38.15898660434554 2014 38.221302618417575 2015 38.96962671147602 2016 38.62523468713078 2017 38.74789964181209 2018 39.08676219877436 2019 39.4982591738133 2020 39.310004094162274 2021 39.37261895699895 2022 39.08728082888402 2023 39.49877644586007