Year	Percent
1960	8.29089
1961	8.34702
1962	8.40275
1963	8.45817
1964	8.51425
1965	8.57026
1966	8.62831
1967	8.68861
1968	8.75172
1969	8.81637
1970	8.89318
1971	9.00034
1972	9.11307
1973	9.23246
1974	9.36326
1975	9.50726
1976	9.66583
1977	9.83709
1978	10.02247
1979	10.22078
1980	10.39104
1981	10.4485
1982	10.51839
1983	10.59817
1984	10.68542
1985	10.77765
1986	10.87449
1987	10.97791
1988	11.09565
1989	11.23607
1990	11.38612
1991	11.44081
1992	11.52724
1993	11.63696
1994	11.75991
1995	11.88873
1996	12.02235
1997	12.16509
1998	12.32637
1999	12.51751
2000	12.76219
2001	13.07956
2002	13.42225
2003	13.78943
2004	14.18024
2005	14.59163
2006	15.02708
2007	15.48798
2008	15.97528
2009	16.48639
2010	17.02409
2011	17.39722
2012	17.7425
2013	18.09782
2014	18.46818
2015	18.85555
2016	19.26115
2017	19.68484