Year	Percent
1960	5.65305
1961	5.701
1962	5.80957
1963	5.92807
1964	6.03941
1965	6.13054
1966	6.20081
1967	6.25657
1968	6.40031
1969	6.61721
1970	6.84778
1971	7.09232
1972	7.35196
1973	7.63123
1974	7.93998
1975	8.28371
1976	8.66875
1977	9.09335
1978	9.55411
1979	10.03972
1980	10.5425
1981	10.7591
1982	10.9719
1983	11.18402
1984	11.40227
1985	11.62948
1986	11.86921
1987	12.11919
1988	12.23209
1989	12.34205
1990	12.44744
1991	12.54621
1992	12.64181
1993	12.74035
1994	12.71666
1995	12.57643
1996	12.45848
1997	12.35929
1998	12.27322
1999	12.19251
2000	12.11196
2001	12.02984
2002	11.94812
2003	11.86939
2004	11.7975
2005	11.73473
2006	11.68155
2007	11.6362
2008	11.59637
2009	11.60651
2010	11.63288
2011	11.65861
2012	11.68436
2013	11.71016
2014	11.73719
2015	11.76592
2016	11.79635
2017	11.82824