Year	Percent
1990	60.17267
1991	60.49731
1992	60.85779
1993	61.61593
1994	61.5577
1995	61.07726
1996	61.76351
1997	61.80516
1998	61.65691
1999	62.10427
2000	62.71355
2001	63.54589
2002	63.8237
2003	64.60564
2004	64.49284
2005	64.86794
2006	64.21335
2007	64.14194
2008	64.79974
2009	66.66234
2010	66.25326
2011	66.1689
2012	66.36577
2013	66.57513
2014	66.93156
2015	66.67546
2016	66.39267
2017	66.28412