Year	Percent
1960	1.8992
1961	1.91375
1962	1.92785
1963	1.94286
1964	1.96007
1965	1.9782
1966	1.99631
1967	2.0134
1968	2.03107
1969	2.04927
1970	2.06722
1971	2.08242
1972	2.09698
1973	2.11507
1974	2.13723
1975	2.161
1976	2.18342
1977	2.19923
1978	2.20427
1979	2.19615
1980	2.1785
1981	2.15958
1982	2.14064
1983	2.11583
1984	2.08445
1985	2.05022
1986	2.01359
1987	1.98152
1988	1.96146
1989	1.95652
1990	1.96184
1991	1.96814
1992	1.97095
1993	1.97317
1994	1.97433
1995	1.97333
1996	1.97242
1997	1.96836
1998	1.95512
1999	1.93057
2000	1.89811
2001	1.86349
2002	1.83063
2003	1.79892
2004	1.76987
2005	1.74289
2006	1.7158
2007	1.68882
2008	1.66391
2009	1.64161
2010	1.62116
2011	1.60132
2012	1.58155
2013	1.56268
2014	1.54465
2015	1.52723
2016	1.51005
2017	1.49248