Year	Percent
1960	2.84525
1961	3.42126
1962	3.86806
1963	4.06077
1964	3.91064
1965	3.56596
1966	3.19861
1967	2.91747
1968	2.55401
1969	2.17116
1970	1.78425
1971	1.35268
1972	0.96472
1973	0.73961
1974	0.71136
1975	0.83998
1976	1.02027
1977	1.15959
1978	1.17694
1979	1.01926
1980	0.76306
1981	0.47839
1982	0.24368
1983	0.09922
1984	0.07249
1985	0.11821
1986	0.20415
1987	0.25354
1988	0.29939
1989	0.27638
1990	0.23569
1991	0.18899
1992	0.17083
1993	0.15486
1994	0.19741
1995	0.25325
1996	0.3045
1997	0.36873
1998	0.42299
1999	0.46835
2000	0.50186
2001	0.5379
2002	0.57939
2003	0.60812
2004	0.6164
2005	0.63044
2006	0.63928
2007	0.65476
2008	0.63108
2009	0.57984
2010	0.51314
2011	0.42163
2012	0.35699
2013	0.35857
2014	0.43011
2015	0.54868
2016	0.71012
2017	0.8348