Year	Percent
1960	0.00711
1961	30.63322
1962	35.08817
1963	40.42273
1964	40.81709
1965	47.46271
1966	51.01456
1967	55.95597
1968	50.78426
1969	59.10537
1970	69.26258
1971	66.50487
1972	63.77132
1973	84.79861
1974	72.32883
1975	70.81074
1976	68.07677
1977	67.32819
1978	55.83877
1979	63.03659
1980	67.69703
1981	70.32136
1982	67.84727
1983	65.83188
1984	68.64416
1985	88.99377
1986	72.36352
1987	72.87151
1988	62.04449
1989	67.14012
1990	84.05251
1991	59.84669
1992	56.81537
1993	69.44306
1994	58.66562
1995	64.97488
1996	65.24001
1997	61.50592
1998	57.16804
1999	52.87673
2000	62.51844
2001	63.33217
2002	57.59803
2003	55.04556
2004	74.34002
2005	93.98725
2006	83.32141
2007	85.97584
2008	93.72551
2009	77.96998
2010	92.29073
2011	100.70931
2012	110.41858
2013	99.50688
2014	84.98045
2015	68.87707
2016	69.64618
2017	76.91896