Year	Percent
1960	2.508
1961	2.64476
1962	2.42507
1963	3.31639
1964	3.34023
1965	3.09835
1966	2.84357
1967	4.70363
1968	2.35737
1969	2.38756
1970	3.50644
1971	3.61952
1972	3.63081
1973	3.92539
1974	3.93296
1975	5.21628
1976	5.67691
1977	8.21439
1978	6.1997
1979	3.35244
1980	4.55907
1981	3.98482
1982	5.11265
1983	4.84596
1984	3.35756
1985	3.87015
1986	3.3493
1987	3.4115
1988	2.1852
1989	2.19048
1990	2.68238
1991	2.01982
1992	2.50704
1993	2.7461
1994	2.4742
1995	2.63532
1996	2.50203
1997	1.99677
1998	2.01666
1999	1.93063
2000	1.71653
2001	1.6839
2002	1.48463
2003	1.46587
2004	1.38222
2005	1.60475
2006	1.46916
2007	1.30394
2008	1.23622
2009	1.52496
2010	1.46673
2011	1.3805
2012	1.48334
2013	1.633
2014	1.58835
2015	1.72582
2016	1.3207
2017	0.97738