Year	Percent
1960	6.05042
1961	6.55738
1962	8
1963	7.8125
1964	8.30769
1965	9.81183
1966	9.6641
1967	7.3076
1968	8.18815
1969	6.62427
1970	7.04866
1971	9.1318
1972	9.55947
1973	9.42623
1974	10.46025
1975	13.73887
1976	13.8193
1977	15.06352
1978	16.60703
1979	12.03078
1980	16.14038
1981	13.29909
1982	17.77822
1983	13.53058
1984	15.80657
1985	17.30935
1986	15.87481
1987	15.66461
1988	14.49244
1989	13.42602
1990	14.64998
1991	14.02175
1992	15.6341
1993	16.74702
1994	9.98251
1995	13.40913
1996	14.37043
1997	13.80978
1998	14.80766
1999	13.17977
2000	13.37598
2001	13.72824
2002	13.48078
2003	13.8584
2004	15.03258
2005	15.77928
2006	16.7955
2007	18.90192
2008	23.97551
2009	23.36495
2010	22.97988
2011	23.20474
2012	25.71051
2013	26.52901
2014	25.29081
2015	26.44123
2016	25.88238
2017	23.37631