Year	Percent
1960	2.31573
1961	2.70243
1962	2.56591
1963	3.19562
1964	2.83587
1965	2.42933
1966	2.67757
1967	2.61765
1968	3.00457
1969	2.39022
1970	2.31601
1971	2.62862
1972	2.84392
1973	3.0618
1974	3.14583
1975	4.60291
1976	6.22043
1977	6.61977
1978	5.83681
1979	5.63346
1980	5.94007
1981	6.38459
1982	6.22087
1983	4.50566
1984	4.01819
1985	5.39044
1986	4.30446
1987	4.36931
1988	4.12852
1989	4.39292
1990	4.14883
1991	4.14284
1992	4.29805
1993	4.65557
1994	4.49382
1995	4.34741
1996	3.94909
1997	4.19266
1998	3.45633
1999	2.90046
2000	2.21096
2001	3.72613
2002	3.49179
2003	3.49421
2004	3.24946
2005	3.258
2006	3.1098
2007	3.04695
2008	3.1835
2009	3.28865
2010	3.3908
2011	3.2975
2012	3.46275
2013	3.80578
2014	3.67784
2015	3.22992
2016	3.21141
2017	3.1529