Year	Percent
1960	40.16088
1961	40.70747
1962	41.58607
1963	43.51536
1964	42.93217
1965	48.98555
1966	53.07937
1967	53.45762
1968	56.77721
1969	52.78667
1970	55.29391
1971	52.35089
1972	49.54147
1973	57.09809
1974	64.89754
1975	61.83941
1976	63.49963
1977	65.18149
1978	67.40425
1979	69.26049
1980	71.66796
1981	60.64905
1982	46.87446
1983	47.9363
1984	48.74962
1985	45.83047
1986	45.39845
1987	38.96448
1988	44.88228
1989	51.29863
1990	61.38305
1991	63.04859
1992	62.9021
1993	74.02108
1994	87.78749
1995	93.2771
1996	102.92922
1997	108.74097
1998	118.43657
1999	117.38875
2000	103.20502
2001	100.11555
2002	104.5196
2003	104.7649
2004	118.11233
2005	119.85688
2006	116.03142
2007	119.51691
2008	120.75393
2009	83.62395
2010	95.783
2011	107.86426
2012	106.48672
2013	101.54646
2014	97.11642
2015	92.10254
2016	85.46782
2017	86.9072