Year	Percent
1960	39.04317
1961	46.24456
1962	19.79387
1963	24.68468
1964	25.08406
1965	22.60394
1966	25.9862
1967	23.43442
1968	23.13563
1969	23.78878
1970	22.07273
1971	18.44252
1972	20.44956
1973	25.50366
1974	38.74904
1975	33.68894
1976	33.05458
1977	30.58657
1978	25.53584
1979	31.1483
1980	34.33846
1981	34.58725
1982	30.92486
1983	27.94181
1984	25.71002
1985	23.58393
1986	12.85476
1987	14.27247
1988	15.50787
1989	18.63926
1990	23.44369
1991	29.11782
1992	25.31959
1993	21.78388
1994	22.53073
1995	26.19478
1996	29.76045
1997	30.90631
1998	22.57835
1999	28.15012
2000	42.06972
2001	36.6893
2002	35.50453
2003	38.24883
2004	40.05323
2005	47.20519
2006	48.81069
2007	47.06816
2008	47.97335
2009	35.37165
2010	38.44455
2011	38.78695
2012	36.89055
2013	33.2099
2014	30.21912
2015	23.18644
2016	21.00176
2017	24.03083