Year	Percent
1960	12.28024
1961	14.00487
1962	12.76343
1963	13.93566
1964	15.57511
1965	14.01775
1966	12.92626
1967	19.83772
1968	18.68624
1969	17.94152
1970	19.50739
1971	18.0325
1972	16.74163
1973	18.5788
1974	19.1246
1975	20.88107
1976	20.67411
1977	31.61102
1978	28.39042
1979	17.27581
1980	14.03675
1981	21.78034
1982	20.0151
1983	31.47465
1984	33.94611
1985	22.07015
1986	29.12453
1987	28.79425
1988	25.0911
1989	27.55135
1990	27.20571
1991	23.59976
1992	22.58419
1993	22.62086
1994	27.54616
1995	42.04935
1996	35.4622
1997	36.96536
1998	35.41964
1999	36.42468
2000	36.09957
2001	50.7796
2002	92.12012
2003	50.82826
2004	71.21292
2005	60.64614
2006	63.35062
2007	63.27592
2008	59.58845
2009	51.87235
2010	56.2973
2011	66.63168
2012	61.44855
2013	52.51024
2014	56.74381
2015	53.70572
2016	45.68619
2017	41.0768