Year	Percent
1960	6.9098
1961	6.02394
1962	6.09901
1963	5.97263
1964	5.74833
1965	5.26962
1966	6.74601
1967	6.01286
1968	4.99804
1969	4.07584
1970	3.92215
1971	4.04699
1972	3.75023
1973	4.77595
1974	6.08763
1975	6.72096
1976	6.1828
1977	6.33472
1978	6.66157
1979	8.26017
1980	9.34801
1981	8.66672
1982	8.23333
1983	7.94044
1984	7.81204
1985	7.73065
1986	7.10128
1987	7.05799
1988	7.53828
1989	8.24281
1990	8.54707
1991	8.5881
1992	9.697
1993	9.92668
1994	10.30357
1995	12.15741
1996	11.67292
1997	12.06155
1998	12.82226
1999	13.51239
2000	14.05856
2001	13.58453
2002	15.41409
2003	15.81879
2004	19.86352
2005	22.66094
2006	24.92783
2007	25.15107
2008	29.49594
2009	26.16147
2010	27.09845
2011	31.08347
2012	31.25929
2013	28.41327
2014	25.95422
2015	22.12225
2016	21.03426
2017	21.77466