Year	Percent
1960	0.75942
1961	0.43382
1962	0.53302
1963	0.91579
1964	1.11115
1965	1.06825
1966	0.83316
1967	0.7109
1968	0.5442
1969	0.43054
1970	0.24365
1971	0.32387
1972	0.52982
1973	0.44952
1974	0.44719
1975	0.41819
1976	0.30561
1977	0.341
1978	0.30298
1979	0.29073
1980	0.30436
1981	0.15868
1982	0.07954
1983	0.09656
1984	0.10081
1985	0.12886
1986	0.13254
1987	0.18102
1988	0.41049
1989	0.45467
1990	0.38647
1991	0.45871
1992	0.48965
1993	0.47347
1994	0.38889
1995	0.28904
1996	0.27183
1997	0.31733
1998	0.28779
1999	0.3003
2000	0.30843
2001	0.40262
2002	0.50484
2003	0.47519
2004	0.48828
2005	0.60448
2006	0.71191
2007	0.78665
2008	0.84124
2009	0.85379
2010	0.96281
2011	1.43497
2012	0.77311
2013	0.53521
2014	0.27936
2015	0.62339
2016	0.55022
2017	0.40095