Year	Percent
1991	52.61
1992	52.8
1993	52.95
1994	53.04
1995	53
1996	53.06
1997	52.98
1998	52.78
1999	52.5
2000	52.23
2001	52.21
2002	52.07
2003	51.96
2004	51.86
2005	51.79
2006	52.02
2007	52.21
2008	52.34
2009	52.27
2010	46.03
2011	47.68
2012	47.73
2013	47.7
2014	47.71
2015	47.62
2016	47.58
2017	47.49
2018	47.31
2019	47.04