Year	Percent
1960	6.6317
1961	6.67613
1962	6.72314
1963	6.77262
1964	6.82489
1965	6.8791
1966	6.93633
1967	6.99702
1968	7.06329
1969	7.13622
1970	7.21819
1971	7.31767
1972	7.42628
1973	7.54172
1974	7.6636
1975	7.7902
1976	7.922
1977	8.0576
1978	8.19658
1979	8.33639
1980	8.29887
1981	8.20928
1982	8.11824
1983	8.02699
1984	7.9374
1985	7.85035
1986	7.767
1987	7.68733
1988	7.61142
1989	7.58543
1990	7.70317
1991	7.82568
1992	7.95468
1993	8.09212
1994	8.2433
1995	8.41078
1996	8.59632
1997	8.79821
1998	9.01691
1999	9.25727
2000	9.53377
2001	9.82439
2002	10.1312
2003	10.45284
2004	10.78878
2005	11.13619
2006	11.49695
2007	11.87033
2008	12.25557
2009	12.64861
2010	13.04958
2011	13.45751
2012	13.87345
2013	14.30082
2014	14.74468
2015	15.20928
2016	15.697
2017	16.20837