Year	Percent
1960	2.70853
1961	2.86178
1962	3.026
1963	3.19954
1964	3.38345
1965	3.57726
1966	3.78268
1967	3.99991
1968	4.22985
1969	4.47152
1970	4.72669
1971	4.91863
1972	5.05377
1973	5.19327
1974	5.336
1975	5.48088
1976	5.62899
1977	5.78249
1978	5.94812
1979	6.13259
1980	6.34277
1981	6.44135
1982	6.53788
1983	6.65385
1984	6.80262
1985	6.99086
1986	7.23004
1987	7.51418
1988	7.81297
1989	8.07614
1990	8.26644
1991	8.36584
1992	8.39128
1993	8.37613
1994	8.3663
1995	8.38903
1996	8.44991
1997	8.53665
1998	8.50112
1999	8.45416
2000	8.39886
2001	8.33411
2002	8.26558
2003	8.19546
2004	8.12735
2005	8.06268
2006	8.00225
2007	7.94492
2008	7.97956
2009	8.03621
2010	8.10868
2011	8.19731
2012	8.30349
2013	8.42657
2014	8.56893
2015	8.73104
2016	8.9145
2017	9.11856