Year	Percent
1960	12.43697
1961	11.47541
1962	9.28
1963	5.9375
1964	12
1965	12.09678
1966	11.27937
1967	10.51203
1968	8.73984
1969	7.67885
1970	11.50523
1971	10.21143
1972	8.28194
1973	11.59836
1974	12.16876
1975	9.17188
1976	14.57895
1977	14.26777
1978	14.781
1979	21.04606
1980	14.43652
1981	9.82551
1982	11.55256
1983	11.58177
1984	12.63143
1985	10.78251
1986	12.58432
1987	7.45005
1988	6.61956
1989	6.13929
1990	5.61461
1991	7.3166
1992	5.56841
1993	5.17525
1994	6.30259
1995	5.15079
1996	6.03137
1997	7.79734
1998	5.58506
1999	6.26039
2000	6.31981
2001	8.46831
2002	7.04118
2003	8.45263
2004	11.12327
2005	11.42612
2006	12.14994
2007	15.66466
2008	12.54915
2009	11.7338
2010	12.03931
2011	13.64542
2012	12.78688
2013	14.09042
2014	14.72211
2015	14.24274
2016	14.92695
2017	18.243