Year	Percent
1960	27.69985
1961	25.88154
1962	29.21388
1963	27.60352
1964	28.32277
1965	27.59815
1966	27.04634
1967	26.08902
1968	27.73465
1969	27.81016
1970	28.35997
1971	30.15087
1972	27.7039
1973	24.55588
1974	27.39097
1975	29.20905
1976	25.67974
1977	29.07267
1978	31.12641
1979	29.88718
1980	24.76411
1981	23.95081
1982	20.56039
1983	18.51022
1984	23.81369
1985	23.65382
1986	20.50156
1987	24.67226
1988	25.95693
1989	26.34045
1990	31.47838
1991	29.4368
1992	26.38488
1993	25.18658
1994	33.45604
1995	35.91884
1996	28.4854
1997	34.1251
1998	32.92584
1999	35.66899
2000	49.54263
2001	45.16663
2002	25.30448
2003	39.46652
2004	61.22044
2005	50.82
2006	50.56143
2007	52.74263
2008	54.07892
2009	49.71503
2010	42.76389
2011	45.44168
2012	46.47354
2013	48.88011
2014	50.81279
2015	49.64203
2016	51.78916
2017	54.83765