Year	Percent
1960	2.67644
1961	2.23291
1962	2.18704
1963	2.42061
1964	3.16355
1965	4.01105
1966	4.72826
1967	4.49703
1968	4.45316
1969	3.92227
1970	5.16527
1971	5.37244
1972	4.9789
1973	3.87224
1974	4.18234
1975	4.72416
1976	3.98077
1977	4.85467
1978	3.71113
1979	3.67052
1980	4.23013
1981	5.78515
1982	5.36762
1983	4.42337
1984	3.75236
1985	3.45166
1986	3.22373
1987	4.1475
1988	2.42611
1989	2.6237
1990	2.5554
1991	3.19928
1992	2.98642
1993	2.87525
1994	2.84712
1995	2.75135
1996	2.40056
1997	2.08556
1998	1.60534
1999	2.10148
2000	1.63468
2001	2.08492
2002	2.21913
2003	2.61481
2004	2.26306
2005	2.17393
2006	2.0076
2007	2.05143
2008	1.91143
2009	1.96028
2010	1.51138
2011	1.57491
2012	1.43341
2013	1.5206
2014	1.45511
2015	1.52886
2016	1.40637
2017	1.12545