Year	Percent
1961	1.85588
1962	1.93219
1963	2.42837
1964	2.92158
1965	3.22994
1966	3.1072
1967	2.48622
1968	2.19562
1969	2.02066
1970	1.88311
1971	1.90607
1972	1.93641
1973	1.92555
1974	2.79458
1975	4.49206
1976	4.13172
1977	3.96778
1978	4.8109
1979	6.88659
1980	8.70858
1981	7.53696
1982	7.53902
1983	7.17962
1984	7.96915
1985	6.8239
1986	6.69724
1987	6.85567
1988	8.50144
1989	10.27665
1990	9.65797
1991	5.70513
1992	3.44171
1993	3.07169
1994	2.86844
1995	2.22562
1996	2.11714
1997	3.34318
1998	7.27694
1999	9.50694
2000	7.61384
2001	4.34902
2002	3.71939
2003	3.26355
2004	3.09944
2005	2.78428
2006	2.28423
2007	1.87744
2008	1.50079
2009	1.19263
2010	1.14248
2011	1.09071
2012	0.86836
2013	0.80642
2014	0.76842
2015	0.74045
2016	0.67079
2017	0.65966