Year	Percent
1990	59.75
1991	59.85
1992	59.76
1993	60
1994	60.64
1995	60.59
1996	61.27
1997	62.18
1998	62.87
1999	63.72
2000	65.28
2001	64.43
2002	66.39
2003	67.74
2004	68.79
2005	70.1
2006	71.1
2007	71.77
2008	72.76
2009	73.16
2010	73.63
2011	73.95
2012	74.29
2013	74.29
2014	74.22
2015	74.38
2016	74.38
2017	74.16
2018	74.06
2019	74.17