Year	Percent
1960	7.31094
1961	7.18014
1962	7.01802
1963	6.75073
1964	6.37656
1965	5.92593
1966	5.4328
1967	4.98992
1968	4.75159
1969	4.75374
1970	4.92119
1971	5.04549
1972	5.10792
1973	4.95716
1974	4.46156
1975	3.74314
1976	2.95788
1977	2.28872
1978	1.85063
1979	1.72915
1980	1.8422
1981	2.05224
1982	2.20623
1983	2.22122
1984	2.02965
1985	1.70555
1986	1.31705
1987	1.03452
1988	1.03016
1989	0.73967
1990	1.41231
1991	2.23534
1992	2.90376
1993	3.16448
1994	2.90786
1995	2.34456
1996	1.60972
1997	1.07608
1998	1.04901
1999	1.49574
2000	2.59703
2001	3.91279
2002	4.87835
2003	5.09215
2004	4.42658
2005	3.30252
2006	1.90854
2007	0.87513
2008	0.76185
2009	1.90525
2010	3.78341
2011	5.80251
2012	7.07889
2013	7.23659
2014	6.19512
2015	4.51487
2016	2.79902
2017	1.43669