Year	Percent
1960	53.18683
1961	64.65345
1962	36.29848
1963	22.74109
1964	20.31056
1965	22.42798
1966	30.25829
1967	31.50684
1968	29.58198
1969	26.70538
1970	24.21052
1971	26.60654
1972	29.08213
1973	31.95365
1974	35.06033
1975	39.11192
1976	31.00389
1977	26.59574
1978	27.33232
1979	25.96074
1980	35.76582
1981	48.16319
1982	59.73239
1983	38.43844
1984	30.39124
1985	30.2843
1986	29.45063
1987	19.72836
1988	18.61912
1989	14.1283
1990	15.90551
1991	20.52816
1992	21.59969
1993	29.49612
1994	54.48614
1995	36.57264
1996	32.79041
1997	22.23338
1998	26.68438
1999	27.77203
2000	22.62595
2001	26.35664
2002	23.4076
2003	26.09032
2004	22.52034
2005	20.19023
2006	21.63246
2007	21.81255
2008	18.30298
2009	22.51301
2010	20.52318
2011	25.2725
2012	25.99645
2013	30.94452
2014	41.3
2015	40.87291
2016	50.4062
2017	26.59091