Year	Percent
1965	28.21882
1966	26.73203
1967	25.65157
1968	24.85358
1969	25.33673
1970	33.30545
1971	30.20853
1972	29.1349
1973	28.13256
1974	30.91312
1975	31.43487
1976	30.53357
1977	26.82064
1978	23.38681
1979	26.14331
1980	27.49182
1981	23.86308
1982	23.42431
1983	23.25546
1984	24.24723
1985	26.59799
1986	24.81398
1987	26.01643
1988	27.26413
1989	30.03692
1990	29.46053
1991	24.95197
1992	22.9436
1993	18.9486
1994	20.25604
1995	20.65353
1996	20.40527
1997	20.21685
1998	21.3364
1999	21.62755
2000	22.75418
2001	22.75014
2002	21.74101
2003	21.57414
2004	21.55762
2005	22.00387
2006	23.02663
2007	24.60886
2008	24.51967
2009	20.92416
2010	22.91268
2011	23.81596
2012	22.61056
2013	22.49484
2014	23.35
2015	24.28524
2016	24.74942
2017	25.68083