Year	Percent
1991	45.55
1992	44.9
1993	44.23
1994	43.62
1995	43.06
1996	43.56
1997	43.98
1998	44.38
1999	44.71
2000	45.75
2001	45.19
2002	44.59
2003	44.02
2004	44.33
2005	44.5
2006	43.89
2007	44.7
2008	44.16
2009	43.16
2010	43.89
2011	45.44
2012	46.92
2013	46.95
2014	47.73
2015	47.2
2016	47.55
2017	47.64
2018	45.83
2019	45.91