Year	%
1971	70.64584
1972	71.12457
1973	72.36371
1974	74.53544
1975	78.4517
1976	75.43615
1977	77.92833
1978	71.29491
1979	77.43132
1980	78.68832
1981	79.38802
1982	81.4167
1983	82.36404
1984	81.9568
1985	84.47843
1986	83.4324
1987	84.04549
1988	85.00072
1989	86.39985
1990	85.52368
1991	88.23168
1992	88.61451
1993	89.12819
1994	89.16702
1995	89.13834
1996	89.42222
1997	89.44371
1998	89.47233
1999	90.44109
2000	90.29134
2001	91.44613
2002	92.94045
2003	93.24123
2004	90.89416
2005	89.63143
2006	91.12443
2007	91.43135
2008	91.5702
2009	90.96729
2010	90.65366
2011	90.02446
2012	86.27514
2013	87.06141
2014	87.88312
2015	89.28333
2016	91.10726
2017	91.62661