Year	Percent
1960	0.67003
1961	0.47108
1962	0.55153
1963	0.56363
1964	0.74712
1965	0.94185
1966	0.95157
1967	0.76723
1968	0.562
1969	0.70275
1970	0.93348
1971	0.6881
1972	0.2955
1973	0.17236
1974	0.29016
1975	0.39728
1976	0.36369
1977	0.35516
1978	0.29115
1979	0.21822
1980	0.203
1981	0.11992
1982	0.05719
1983	0.04527
1984	0.09087
1985	0.16517
1986	0.23257
1987	0.33368
1988	0.4596
1989	0.66718
1990	0.7726
1991	0.68164
1992	0.58653
1993	0.58084
1994	0.71071
1995	0.5247
1996	0.15915
1997	0.05726
1998	0.05551
1999	0.07793
2000	0.16058
2001	0.26847
2002	0.32544
2003	0.37209
2004	0.3933
2005	0.39994
2006	0.56248
2007	0.74155
2008	0.77903
2009	0.8519
2010	0.85252
2011	0.75515
2012	0.73976
2013	0.84735
2014	0.99222
2015	1.05745
2016	1.25645
2017	1.44728