Year	Percent
1960	7.60405
1961	5.99495
1962	9.38368
1963	7.89045
1964	5.56371
1965	4.15058
1966	4.98969
1967	4.99706
1968	5.40371
1969	6.39871
1970	4.73588
1971	6.60796
1972	6.83788
1973	5.7095
1974	6.28901
1975	5.97867
1976	5.9215
1977	7.32639
1978	5.71541
1979	6.32977
1980	6.4837
1981	7.37193
1982	6.52099
1983	5.83615
1984	4.75649
1985	6.27333
1986	6.32406
1987	7.57576
1988	6.21185
1989	6.57939
1990	4.63132
1991	6.07801
1992	8.13279
1993	9.3138
1994	10.60432
1995	10.09101
1996	11.07782
1997	12.77535
1998	12.93443
1999	11.5555
2000	11.63611
2001	10.27329
2002	13.3701
2003	14.71378
2004	16.84503
2005	17.30539
2006	17.40679
2007	18.28242
2008	18.34177
2009	14.49614
2010	16.03719
2011	16.75695
2012	14.28868
2013	14.71676
2014	14.00132
2015	11.78057
2016	13.53808
2017	13.83582