Year	Percent
1990	57.97
1991	58.2
1992	58.47
1993	58.69
1994	58.91
1995	59.44
1996	60.02
1997	60.57
1998	60.6
1999	60.59
2000	60.56
2001	60.51
2002	60.42
2003	60.3
2004	60.16
2005	60
2006	60.79
2007	61.09
2008	61.63
2009	62.72
2010	61.91
2011	62.51
2012	62.29
2013	62.57
2014	62.92
2015	63.29
2016	63.15
2017	63.06
2018	63.01
2019	62.98