Year	Percent
1990	59.36514
1991	61.1308
1992	61.78715
1993	62.45218
1994	62.41374
1995	62.32745
1996	62.3773
1997	63.3349
1998	63.53119
1999	64.25562
2000	64.30555
2001	64.12866
2002	63.95298
2003	64.27005
2004	64.28195
2005	64.39211
2006	63.73766
2007	64.41038
2008	64.54139
2009	64.20303
2010	65.81178
2011	64.81012
2012	65.36137
2013	66.40413
2014	65.838
2015	67.37315
2016	68.27141
2017	66.96711