Year	Percent
1960	14.95583
1961	13.87458
1962	13.63789
1963	13.11557
1964	12.68247
1965	12.38608
1966	11.52928
1967	10.89277
1968	10.94687
1969	10.80665
1970	10.875
1971	9.97796
1972	9.76263
1973	10.96908
1974	12.51981
1975	10.77727
1976	10.61006
1977	11.80287
1978	13.76951
1979	15.65658
1980	20.6717
1981	20.70084
1982	24.05951
1983	25.81421
1984	26.07274
1985	24.86711
1986	30.42081
1987	33.72013
1988	32.81186
1989	32.09792
1990	32.07301
1991	30.02431
1992	30.36482
1993	23.85158
1994	27.06785
1995	42.76052
1996	45.73967
1997	44.67336
1998	46.82455
1999	47.0609
2000	48.85265
2001	43.8197
2002	43.22834
2003	46.67735
2004	49.88749
2005	50.4227
2006	52.63926
2007	53.39311
2008	54.91663
2009	52.35596
2010	57.52594
2011	60.19849
2012	62.54711
2013	60.49548
2014	61.5111
2015	67.18665
2016	71.63584
2017	73.19187