Year	%
1975	63.56614
1976	62.7606
1977	61.43542
1978	60.87796
1979	60.63257
1980	59.57017
1981	56.90433
1982	56.98413
1983	55.43018
1984	54.11128
1985	56.61018
1986	58.12571
1987	58.60602
1988	60.41792
1989	61.037
1990	61.2133
1991	60.5421
1992	60.26746
1993	59.13954
1994	59.98958
1995	60.92185
1996	61.64436
1997	61.35349
1998	62.37761
1999	61.58784
2000	63.20422
2001	65.43672
2002	66.62194
2004	70.43929
2005	71.5125
2006	72.4972
2007	74.19931
2008	73.71195
2009	74.36677
2010	75.24069
2011	76.05966
2012	75.29551
2013	75.96678
2014	76.10151
2015	76.30307
2016	75.92435