Year	Percent
1960	2.06594
1961	2.088
1962	2.11298
1963	2.14281
1964	2.17886
1965	2.21808
1966	2.42754
1967	2.65724
1968	2.60753
1969	2.20398
1970	1.6663
1971	0.74538
1972	0.13528
1973	0.88773
1974	3.40667
1975	6.73728
1976	10.02453
1977	11.81372
1978	11.53786
1979	9.43198
1980	6.58923
1981	3.79166
1982	1.67519
1983	0.35331
1984	0.11435
1985	0.64675
1986	1.3986
1987	1.88042
1988	2.07554
1989	1.84082
1990	1.34639
1991	0.78891
1992	0.43639
1993	0.41666
1994	0.84937
1995	1.5821
1996	2.40432
1997	3.05811
1998	3.44116
1999	3.47542
2000	3.28535
2001	3.05279
2002	2.89964
2003	2.8066
2004	2.80514
2005	2.86188
2006	2.91945
2007	2.94437
2008	2.95168
2009	2.93569
2010	2.90606
2011	2.87454
2012	2.85337
2013	2.84674
2014	2.85829
2015	2.88121
2016	2.90437
2017	2.92188