Year	Percent
1991	47.99
1992	47.55
1993	46.97
1994	48.37
1995	49.7
1996	51.05
1997	52.74
1998	54.31
1999	53.68
2000	53.1
2001	52.5
2002	51.71
2003	50.91
2004	50.12
2005	49.31
2006	51.21
2007	52.72
2008	53.8
2009	49.19
2010	44.48
2011	46.55
2012	48.01
2013	47.06
2014	46.12
2015	45.08
2016	44.05
2017	42.98
2018	41.78
2019	41.23