Year	Percent
1990	53.8
1991	54.91
1992	55.49
1993	55.54
1994	55.39
1995	54.92
1996	54.52
1997	54.63
1998	54.39
1999	53.75
2000	53.45
2001	53.29
2002	53.13
2003	53.06
2004	52.82
2005	51.88
2006	51.52
2007	52.26
2008	53.26
2009	53.43
2010	54.16
2011	54.09
2012	54.43
2013	54.42
2014	55.63
2015	55.72
2016	55.95
2017	55.93
2018	56.62
2019	57.74