Year	Percent
1960	4.94369
1961	4.99002
1962	5.03542
1963	5.07964
1964	5.12296
1965	5.16465
1966	5.21083
1967	5.28769
1968	5.36429
1969	5.43949
1970	5.51402
1971	5.58758
1972	5.69083
1973	5.79365
1974	5.89741
1975	6.00365
1976	6.13008
1977	6.25755
1978	6.38742
1979	6.51949
1980	6.65439
1981	6.79061
1982	6.92968
1983	7.07184
1984	7.21851
1985	7.36867
1986	7.52405
1987	7.68363
1988	7.84671
1989	8.0101
1990	8.17422
1991	8.33853
1992	8.50387
1993	8.668
1994	8.68192
1995	8.67836
1996	8.67165
1997	8.6616
1998	8.65104
1999	8.64164
2000	8.63512
2001	8.6308
2002	8.5965
2003	8.56521
2004	8.53719
2005	8.51142
2006	8.70418
2007	8.90546
2008	9.11501
2009	9.33117
2010	9.55608
2011	9.78943
2012	10.032
2013	10.28126
2014	10.53871
2015	10.80331
2016	11.07598
2017	11.35647