Year	Percent
1960	7.60405
1961	5.99495
1962	4.69184
1963	7.89045
1964	5.56372
1965	6.22587
1966	6.65292
1967	7.4956
1968	6.48445
1969	6.39871
1970	5.60157
1971	6.00723
1972	7.19777
1973	7.61267
1974	6.90257
1975	5.82405
1976	9.17539
1977	9.61589
1978	8.60839
1979	6.51092
1980	5.06197
1981	6.92105
1982	9.09049
1983	9.15152
1984	7.5899
1985	11.7361
1986	8.16198
1987	7.87321
1988	9.53161
1989	13.05841
1990	10.35954
1991	7.67504
1992	6.59819
1993	6.90935
1994	7.52991
1995	9.68049
1996	10.42854
1997	10.5608
1998	10.41552
1999	9.82716
2000	10.9864
2001	11.57913
2002	28.38265
2003	25.93091
2004	23.84762
2005	23.24588
2006	23.02669
2007	22.66275
2008	22.0609
2009	19.56099
2010	18.93382
2011	18.44921
2012	16.23786
2013	14.61717
2014	14.40548
2015	10.70565
2016	12.58383
2017	11.17876