Year	Percent
1965	27.90698
1966	25.2882
1967	25.19298
1968	22.92614
1969	22.44536
1970	21.14876
1971	21.51611
1972	22.71663
1973	21.28029
1974	25.80437
1975	28.01769
1976	30.65701
1977	30.54428
1978	30.75808
1979	29.42847
1980	29.36026
1981	32.32821
1982	31.72717
1983	33.49623
1984	35.8992
1985	30.16257
1986	26.60047
1987	23.48388
1988	20.70988
1989	23.91162
1990	27.06806
1991	25.98846
1992	29.19421
1993	29.23958
1994	24.6443
1995	24.70062
1996	25.01377
1997	24.45889
1998	24.91713
1999	24.62026
2000	26.0827
2001	26.17926
2002	23.81054
2003	23.32324
2004	23.27839
2005	21.67944
2006	23.44873
2007	23.83607
2008	26.04989
2009	25.14733
2010	26.64747
2011	23.52013
2012	24.89037
2013	23.19817
2014	23.54222
2015	20.33295
2016	19.67596