Year	Percent
1991	42.32
1992	42.51
1993	41.6
1994	42.44
1995	41.35
1996	41.83
1997	41.62
1998	41.26
1999	42.67
2000	41.98
2001	41.39
2002	40.61
2003	40.6
2004	41.37
2005	41.4
2006	42.11
2007	43.9
2008	43.91
2009	44.22
2010	44.81
2011	43.02
2012	42.96
2013	43.09
2014	43.09
2015	41.67
2016	41.78
2017	40.95
2018	40.52
2019	40.47
2020	38.51