Year	Percent
1991	57.73
1992	55.36
1993	52.16
1994	50.3
1995	48.44
1996	46.14
1997	45.44
1998	46.17
1999	47.05
2000	46.79
2001	46.7
2002	45.27
2003	43.96
2004	41.35
2005	42.16
2006	43.86
2007	45.92
2008	47.19
2009	46.35
2010	46.42
2011	47.65
2012	46.22
2013	46.39
2014	45.6
2015	45.11
2016	45.62
2017	46.32
2018	47.07
2019	48.44