Year	Percent
1960	14.5589
1961	13.31611
1962	14.61622
1963	16.70563
1964	15.53579
1965	14.23184
1966	14.31612
1967	15.11524
1968	15.11469
1969	15.7003
1970	16.34076
1971	15.63755
1972	16.01897
1973	14.84834
1974	12.70947
1975	12.0936
1976	11.22361
1977	9.375
1978	7.91995
1979	9.95599
1980	10.58111
1981	9.61913
1982	9.93506
1983	10.59799
1984	8.45832
1985	5.74666
1986	4.74029
1987	5.52233
1988	3.79551
1989	5.34138
1990	4.02139
1991	3.33503
1992	5.24608
1993	4.23038
1994	4.69056
1995	4.96947
1996	7.45483
1997	5.34363
1998	6.70209
1999	7.77941
2000	15.98456
2001	11.39786
2002	13.979
2003	14.82786
2004	17.75796
2005	19.17816
2006	19.07366
2007	21.88656
2008	24.09554
2009	15.96881
2010	19.7435
2011	17.56763
2012	9.21919
2013	8.84055
2014	8.14913
2015	8.18223
2016	9.82885
2017	9.69182