Year	Percent
1990	50.16
1991	50.38
1992	50.66
1993	50.97
1994	51.28
1995	51.57
1996	52.24
1997	52.89
1998	53.56
1999	54.3
2000	55.14
2001	55.22
2002	55.47
2003	55.86
2004	56.35
2005	56.9
2006	57.23
2007	57.69
2008	58.3
2009	59.06
2010	61.27
2011	63.61
2012	66
2013	68.39
2014	70.72
2015	70.55
2016	69.87
2017	70.75
2018	71.53
2019	72.12