Year	Percent
1990	60.85
1991	61.33
1992	61.81
1993	61.66
1994	61.72
1995	61.4
1996	60.92
1997	60.46
1998	60.01
1999	59.54
2000	59.06
2001	58.62
2002	58.17
2003	57.7
2004	57.23
2005	56.76
2006	55.94
2007	55.11
2008	54.26
2009	53.39
2010	52.5
2011	51.58
2012	50.65
2013	49.71
2014	49.1
2015	48.49
2016	48
2017	47.5
2018	47.07
2019	46.6