Year	Percent
1990	61.34
1991	61.42
1992	61.04
1993	60.64
1994	60.29
1995	59.94
1996	60.53
1997	61.1
1998	61.67
1999	62.21
2000	63.03
2001	63.18
2002	63.35
2003	63.52
2004	63.69
2005	63.85
2006	64.03
2007	64.61
2008	65.19
2009	65.76
2010	66.32
2011	66.88
2012	67.44
2013	67.99
2014	68.52
2015	68.77
2016	69.02
2017	69.26
2018	69.4
2019	69.53