Year	Percent
1970	0.87868
1971	0.78316
1972	0.39466
1973	0.8267
1974	0.70661
1975	0.52092
1976	0.82162
1977	0.39981
1978	0.64211
1979	0.98988
1980	1.07539
1981	1.2308
1982	1.09427
1983	1.47245
1984	0.87797
1985	1.0755
1986	1.57292
1987	0.84413
1988	1.09804
1989	1.24901
1990	0.97027
1991	1.50801
1992	1.20817
1993	0.87651
1994	2.07886
1995	2.64565
1996	2.23507
1997	2.56384
1998	2.42293
1999	2.31252
2000	2.59671
2001	3.97248
2002	3.11552
2003	2.49864
2004	3.18522
2005	2.96511
2006	2.11851
2007	3.14158
2008	2.90003
2009	2.16263
2010	1.98481
2011	2.06216
2012	1.47444
2013	3.73333
2014	2.35538
2015	3.14423
2016	3.28886
2017	2.79384