Year	%
1970	73.76958
1971	73.62477
1972	73.96177
1973	66.50149
1974	66.64607
1975	67.5093
1976	67.53996
1977	67.72978
1978	67.0695
1979	66.75185
1980	65.84167
1981	61.97541
1982	63.45798
1983	64.30564
1984	64.82507
1985	66.191
1986	65.76646
1987	65.77128
1988	65.43697
1989	65.40984
1990	64.96966
1991	65.54475
1992	66.02263
1993	65.15537
1994	66.8825
1995	67.81413
1996	68.96469
1997	69.92132
1998	70.83227
1999	71.42786
2000	71.93066
2001	71.01089
2002	74.25014
2003	76.32754
2004	75.8021
2005	76.41014
2006	77.05695
2007	77.27399
2008	77.93789
2009	78.44062
2010	78.68712
2011	77.96688
2012	75.538
2013	76.31288
2014	76.50319
2015	76.62294
2016	77.33553
2017	76.63144