Year	Percent
1960	5.70509
1961	5.9037
1962	5.9982
1963	5.80353
1964	5.24681
1965	4.4637
1966	3.57429
1967	2.82582
1968	2.46346
1969	2.62965
1970	3.21996
1971	3.94591
1972	4.5406
1973	4.86935
1974	4.85182
1975	4.57868
1976	4.2435
1977	3.98709
1978	3.83984
1979	3.84748
1980	3.95096
1981	4.07579
1982	4.13664
1983	4.06339
1984	3.81266
1985	3.43289
1986	3.01836
1987	2.65632
1988	2.41496
1989	2.33797
1990	2.39242
1991	2.44177
1992	2.3515
1993	2.33872
1994	2.22682
1995	2.03628
1996	1.82704
1997	1.6485
1998	1.5475
1999	1.53339
2000	1.59441
2001	2.12128
2002	2.08073
2003	2.03672
2004	1.08099
2005	0.69042
2006	0.66394
2007	0.67165
2008	0.70829
2009	0.73778
2010	0.70218
2011	0.62127
2012	0.59779
2013	0.61031
2014	0.60832
2015	0.56655
2016	0.53081
2017	0.53381