Year	Percent
1990	43.71
1991	44.11
1992	44.43
1993	44.83
1994	45.04
1995	45.57
1996	45.92
1997	46.23
1998	46.54
1999	46.87
2000	45.97
2001	45.12
2002	44.31
2003	43.54
2004	42.82
2005	42.13
2006	41.49
2007	40.89
2008	40.33
2009	39.84
2010	39.41
2011	38.63
2012	37.96
2013	37.37
2014	36.83
2015	37.3
2016	37.63
2017	37.91
2018	38.13
2019	38.33
2020	38.13