Year	%
1975	63.5471
1976	62.74241
1977	61.41783
1978	60.86097
1979	60.61805
1980	59.55582
1981	56.89181
1982	56.97291
1983	55.41856
1984	54.10004
1985	56.59962
1986	58.11465
1987	58.59557
1988	60.40878
1989	61.02766
1990	61.20338
1991	60.53215
1992	60.25878
1993	59.13101
1994	59.98189
1995	60.91361
1996	61.6359
1997	61.3461
1998	62.37066
1999	61.58096
2000	63.19775
2001	65.4307
2002	66.61628
2004	70.43501
2005	71.50834
2006	72.49356
2007	74.1961
2008	73.70923
2009	74.36446
2010	75.23854
2011	76.0577
2012	75.29385
2013	75.9649
2014	76.09954
2015	76.30108
2016	75.92235