Year	Percent
1960	4.15464
1961	3.51733
1962	3.64902
1963	3.7013
1964	3.65431
1965	3.52349
1966	3.37933
1967	3.26744
1968	3.21992
1969	3.23674
1970	3.17165
1971	2.79935
1972	2.88002
1973	2.89489
1974	2.8283
1975	2.71252
1976	2.56807
1977	2.44229
1978	2.40154
1979	2.46446
1980	2.5927
1981	2.7476
1982	2.81129
1983	2.12422
1984	1.96379
1985	1.6999
1986	1.40253
1987	1.15943
1988	1.01416
1989	1.00609
1990	1.09732
1991	1.22684
1992	1.36516
1993	1.42535
1994	1.44585
1995	1.4412
1996	1.43608
1997	1.43542
1998	1.4128
1999	1.36096
2000	1.29512
2001	1.21564
2002	1.06587
2003	0.98646
2004	0.95579
2005	0.93364
2006	0.92049
2007	0.89902
2008	0.87765
2009	0.84697
2010	0.81378
2011	0.78244
2012	0.77942
2013	0.78184
2014	0.78948
2015	0.7986
2016	0.8096
2017	0.81684