Year	Percent
1965	27.54692
1966	29.05331
1967	28.53529
1968	28.10027
1969	27.64219
1970	26.96668
1971	27.27149
1972	27.54765
1973	27.96848
1974	35.02087
1975	35.17344
1976	32.01672
1977	32.5516
1978	31.34315
1979	32.66767
1980	28.75955
1981	31.68292
1982	30.3127
1983	30.87142
1984	30.83408
1985	30.208
1986	27.39927
1987	27.6076
1988	27.73241
1989	27.34695
1990	27.59814
1991	26.01616
1992	26.37224
1993	26.47452
1994	25.164
1995	26.33118
1996	25.621
1997	27.3224
1998	25.73789
1999	26.10187
2000	26.95991
2001	25.40347
2002	25.23023
2003	25.99722
2004	26.61489
2005	26.15394
2006	25.15394
2007	24.66604
2008	26.76429
2009	24.23823
2010	25.65738
2011	26.61214
2012	26.40736
2013	26.1685
2014	26.42547
2015	25.8309
2016	26.05295
2017	25.57564