Year	Percent
1960	41.66223
1961	44.56301
1962	46.61836
1963	46.72727
1964	46.25569
1965	45.25784
1966	40.50263
1967	39.83371
1968	40.09519
1969	40.54401
1970	44.83107
1971	43.063
1972	44.88873
1973	43.80937
1974	36.90993
1975	40.54839
1976	43.00692
1977	42.26209
1978	44.50714
1979	44.34227
1980	43.89231
1981	44.62066
1982	49.30339
1983	52.6426
1984	51.79078
1985	54.3716
1986	56.50393
1987	59.19273
1988	56.15471
1989	57.57207
1990	62.32295
1991	72.13919
1992	71.06607
1993	63.34454
1994	52.34544
1995	49.46811
1996	49.44728
1997	54.31943
1998	68.24868
1999	57.14987
2000	57.95762
2001	56.44025
2002	56.68067
2003	56.08295
2004	54.24407
2005	52
2006	45.0458
2007	44.37415
2008	43.79253
2009	47.32092
2010	47.84458
2011	46.6233
2012	47.32262
2013	50.42695
2014	52.26668
2015	55.78194
2016	54.3144
2017	53.18576