Year	Percent
1990	53.89
1991	53.66
1992	53.66
1993	53.5
1994	53.36
1995	53.03
1996	52.7
1997	52.45
1998	52.13
1999	51.79
2000	51.6
2001	51.45
2002	51.34
2003	51.11
2004	50.95
2005	50.66
2006	50.58
2007	49.13
2008	47.64
2009	46.12
2010	44.58
2011	43.03
2012	41.47
2013	39.89
2014	38.31
2015	38.19
2016	38.04
2017	37.86
2018	37.66
2019	37.46