Year	Percent
1965	25.64956
1966	26.23796
1967	26.97163
1968	27.40529
1969	27.91197
1970	30.60471
1971	29.64308
1972	29.788
1973	29.65618
1974	30.84838
1975	30.53219
1976	30.37365
1977	30.96428
1978	30.80978
1979	31.17602
1980	31.0685
1981	30.69995
1982	30.48498
1983	32.61663
1984	32.12692
1985	31.97278
1986	32.12168
1987	34.31453
1988	29.49574
1989	26.93349
1990	26.00198
1991	25.64242
1992	25.69403
1993	32.48256
1994	32.14311
1995	32.69208
1996	33.94722
1997	34.19829
1998	33.88376
1999	34.12433
2000	34.20971
2001	33.21734
2002	32.71036
2003	31.19108
2004	32.85106
2005	32.78341
2006	34.19528
2007	33.83514
2008	34.75619
2009	31.89409
2010	32.36191
2011	33.5568
2012	33.77647
2013	31.85632
2014	31.49477
2015	29.98462
2016	29.33244
2017	29.93159