Year	Percent
1960	0.95098
1961	1.46785
1962	2.25484
1963	2.06461
1964	2.69561
1965	2.63083
1966	2.70487
1967	2.78802
1968	2.76118
1969	2.60848
1970	2.33375
1971	2.45819
1972	2.37267
1973	2.64691
1974	3.0852
1975	3.87495
1976	4.72799
1977	5.26333
1978	4.5622
1979	3.86307
1980	3.30463
1981	3.63813
1982	3.61409
1983	3.60465
1984	3.69561
1985	3.69833
1986	3.82058
1987	4.19217
1988	4.62376
1989	4.35788
1990	3.89635
1991	3.22263
1992	2.81765
1993	2.49552
1994	2.56197
1995	2.11786
1996	1.75588
1997	1.58213
1998	1.38317
1999	1.27205
2000	1.38729
2001	1.48316
2002	1.52931
2003	1.46881
2004	1.35573
2005	1.38377
2006	1.29075
2007	1.17752
2008	1.14584
2009	1.214
2010	1.11581
2011	1.10326
2012	1.13279
2013	1.12327
2014	1.10973
2015	1.09928
2016	1.07669
2017	1.04749