Year	Percent
1990	59.33
1991	59.81
1992	60.35
1993	60.97
1994	61.23
1995	61.28
1996	61.49
1997	61.79
1998	61.91
1999	62.1
2000	62.37
2001	62.59
2002	62.64
2003	62.62
2004	62.55
2005	62.5
2006	61.58
2007	60.65
2008	59.72
2009	58.78
2010	57.85
2011	56.91
2012	55.98
2013	55.89
2014	55.74
2015	55.64
2016	55.69
2017	55.67
2018	55.55
2019	55.44