Year	Percent
1991	43.11
1992	43.26
1993	43.31
1994	43.05
1995	43.34
1996	43.07
1997	43.25
1998	43.15
1999	43.22
2000	43.47
2001	43.99
2002	44.19
2003	44.49
2004	45.23
2005	44.96
2006	45.35
2007	45.27
2008	45.02
2009	45.34
2010	45.29
2011	45.38
2012	44.76
2013	44.31
2014	43.36
2015	42.71
2016	42.04
2017	41.31
2018	41.3
2019	41.28
2020	38.3