Year	Percent
1991	45.04
1992	46.1
1993	46.73
1994	46.35
1995	45.45
1996	44.98
1997	44.96
1998	44.97
1999	45.13
2000	45.15
2001	45.23
2002	45.37
2003	45.52
2004	45.71
2005	45.86
2006	46.83
2007	48.08
2008	49.61
2009	50.97
2010	52.15
2011	51.94
2012	51.27
2013	50.21
2014	49.17
2015	48.37
2016	48.08
2017	48.1
2018	49.63
2019	49.57