Year	Percent
1991	65.52958
1992	66.13274
1993	65.00113
1994	65.38766
1995	65.30087
1996	66.92515
1997	66.91725
1998	67.02308
1999	66.41325
2000	66.25557
2001	62.03813
2002	64.02719
2003	62.1983
2004	63.62109
2005	62.3852
2006	62.59731
2007	63.28235
2008	63.75564
2009	64.23489
2010	64.92531
2011	64.96947
2012	68.99854
2013	69.77229
2014	69.84805
2016	72.10636
2017	73.02893