Year	Percent
1960	2.34145
1961	2.46908
1962	2.56757
1963	2.51634
1964	2.53586
1965	2.46796
1966	2.53079
1967	2.38237
1968	2.17652
1969	2.19792
1970	2.10335
1971	2.05253
1972	1.96813
1973	1.86145
1974	1.87597
1975	1.90075
1976	2.16258
1977	2.02209
1978	1.96736
1979	2.0398
1980	1.67861
1981	1.6628
1982	1.72819
1983	1.74881
1984	1.70125
1985	1.82497
1986	1.66102
1987	1.56187
1988	1.56481
1989	1.52417
1990	1.57215
1991	1.53782
1992	1.52371
1993	1.36696
1994	1.33228
1995	1.3555
1996	1.28376
1997	1.22086
1998	1.1852
1999	1.08621
2000	1.02855
2001	0.99175
2002	0.95601
2003	0.92599
2004	0.88997
2005	0.85254
2006	0.77222
2007	0.73405
2008	0.7401
2009	0.74871
2010	0.70563
2011	0.71087
2012	0.68766
2013	0.73077
2014	0.65037
2015	0.66569
2016	0.6836
2017	0.68363