Year	Percent
1960	2.51059
1961	2.02637
1962	1.48407
1963	0.98944
1964	0.85931
1965	0.85199
1966	0.85664
1967	0.94329
1968	1.28267
1969	2.24548
1970	3.52827
1971	4.6684
1972	5.63115
1973	6.19701
1974	6.41096
1975	6.28629
1976	6.16042
1977	6.0995
1978	5.75557
1979	5.20297
1980	4.54422
1981	3.80611
1982	3.32144
1983	3.11976
1984	3.49565
1985	4.06861
1986	4.74257
1987	5.23322
1988	5.46664
1989	5.34739
1990	5.05991
1991	4.69797
1992	4.44335
1993	4.43248
1994	4.80152
1995	5.2404
1996	5.71865
1997	5.96419
1998	5.84592
1999	5.33474
2000	4.61214
2001	3.83328
2002	3.23012
2003	2.84267
2004	2.72392
2005	2.75869
2006	2.85667
2007	2.86088
2008	2.76431
2009	2.52427
2010	2.23717
2011	1.91288
2012	1.6547
2013	1.46343
2014	1.36293
2015	1.32792
2016	1.32863
2017	1.29821