Year	Percent
1991	61.17
1992	61.56
1993	58.66
1994	59.2
1995	57.95
1996	55.4
1997	54
1998	54.2
1999	54.99
2000	52.79
2001	51.59
2002	51.97
2003	50.62
2004	49.03
2005	51.66
2006	52.41
2007	53.98
2008	54.55
2009	53.21
2010	52.79
2011	53.9
2012	53.71
2013	53.18
2014	52.21
2015	51.53
2016	51.07
2017	50.46
2018	51.06
2019	51.32