Year	Percent
1990	49.47
1991	49.68
1992	49.94
1993	50.25
1994	50.55
1995	50.84
1996	51.47
1997	52.1
1998	52.74
1999	53.45
2000	54.26
2001	54.08
2002	54.07
2003	54.2
2004	54.43
2005	54.75
2006	54.89
2007	55.17
2008	55.62
2009	56.24
2010	58.44
2011	60.85
2012	63.31
2013	65.79
2014	68.2
2015	68.16
2016	67.62
2017	68.53
2018	69.36
2019	70.02
2020	67.74