Year	Percent
1991	67.23326
1992	66.33349
1993	66.47047
1994	66.28913
1995	66.43389
1996	66.95235
1997	67.35994
1998	67.79944
1999	69.14141
2000	69.44963
2001	70.9912
2002	71.11365
2003	71.31417
2004	71.74018
2005	71.94312
2006	71.57869
2007	72.06798
2008	72.19787
2009	72.10144
2010	72.13978
2011	71.43808
2012	71.39867
2013	71.54068
2014	72.6073
2015	73.21154
2016	73.772
2017	73.63738