Year	Percent
1965	26.9157
1966	26.3691
1967	26.75467
1968	26.6021
1969	26.93675
1970	27.63994
1971	27.73116
1972	28.75737
1973	30.52147
1974	30.00583
1975	29.21813
1976	30.83341
1977	30.30185
1978	29.96425
1979	29.52355
1980	31.58885
1981	30.6036
1982	30.8827
1983	31.50062
1984	33.26229
1985	34.60371
1986	36.17395
1987	34.74813
1988	36.23323
1989	36.94435
1990	36.72945
1991	36.2975
1992	34.24776
1993	35.1698
1994	29.00004
1995	29.06847
1996	28.42303
1997	27.00545
1998	26.32878
1999	26.63367
2000	27.30577
2001	27.22282
2002	27.52901
2003	28.90378
2004	29.72589
2005	30.00858
2006	30.77745
2007	30.63177
2008	32.42162
2009	31.7083
2010	32.02006
2011	34.27231
2012	34.57214
2013	34.16074
2014	32.7145
2015	30.53851
2016	29.71843
2017	29.24599