Year	Percent
1960	1.30369
1961	1.39849
1962	1.4905
1963	1.58406
1964	1.68097
1965	1.77805
1966	1.87428
1967	1.96216
1968	2.03676
1969	2.09396
1970	2.1406
1971	2.18154
1972	2.22579
1973	2.27735
1974	2.34056
1975	2.4101
1976	2.48058
1977	2.54463
1978	2.60167
1979	2.64876
1980	2.68945
1981	2.73226
1982	2.77736
1983	2.81745
1984	2.85181
1985	2.88526
1986	2.90254
1987	2.9255
1988	2.98865
1989	3.10077
1990	3.23506
1991	3.37716
1992	3.479
1993	3.50077
1994	3.42606
1995	3.29361
1996	3.14532
1997	3.02838
1998	2.95861
1999	2.95175
2000	2.98399
2001	3.02378
2002	3.04308
2003	3.03967
2004	3.00534
2005	2.95238
2006	2.89753
2007	2.85407
2008	2.82352
2009	2.80934
2010	2.80611
2011	2.80342
2012	2.79704
2013	2.79025
2014	2.78229
2015	2.77298
2016	2.76353
2017	2.7523