Year	Percent
1965	23.14178
1966	24.84293
1967	24.65069
1968	24.62763
1969	25.02001
1970	24.26297
1971	24.80693
1972	25.58162
1973	24.27755
1974	25.13266
1975	26.51636
1976	23.99711
1977	22.90423
1978	25.02462
1979	23.65373
1980	21.94541
1981	22.47876
1982	22.1595
1983	22.34853
1984	22.56262
1985	23.35691
1986	22.69277
1987	25.5854
1988	25.37956
1989	26.51534
1990	23.30755
1991	22.99988
1992	24.94461
1993	26.26699
1994	26.18325
1995	25.48295
1996	25.41826
1997	25.21703
1998	26.18313
1999	26.87415
2000	26.87772
2001	27.07795
2002	27.27514
2003	26.95253
2004	25.60392
2005	24.47133
2006	24.47177
2007	24.52192
2008	25.88128
2009	24.96999
2010	25.27592
2011	26.19545
2012	26.58938
2013	26.07604
2014	25.8157
2015	24.37875
2016	24.1386
2017	24.75986