Year	Percent
1960	0.78724
1961	0.91153
1962	1.22493
1963	1.03901
1964	1.1199
1965	1.13767
1966	0.71988
1967	0.3289
1968	0.2549
1969	0.49009
1970	0.49389
1971	0.95366
1972	1.21304
1973	1.10467
1974	1.30406
1975	1.09245
1976	0.49494
1977	0.17366
1978	0.17944
1979	0.23425
1980	0.35598
1981	0.29477
1982	0.08211
1983	0.02653
1984	0.10279
1985	0.19326
1986	0.44867
1987	0.64808
1988	0.72561
1989	0.97263
1990	1.25175
1991	1.33968
1992	1.32835
1993	1.34239
1994	1.36184
1995	1.40474
1996	1.36114
1997	1.2535
1998	1.24387
1999	1.35062
2000	1.34408
2001	1.19046
2002	1.04766
2003	1.2152
2004	1.42133
2005	1.53005
2006	1.59505
2007	1.54439
2008	1.7875
2009	1.85178
2010	1.82541
2011	2.22266
2012	2.40154
2013	2.31118
2014	2.35698
2015	2.35995
2016	2.15531
2017	2.95164