Year	Percent
1971	0.03033
1972	0.00922
1973	0.01445
1974	0.07186
1975	0.01843
1976	0.02015
1977	0.05488
1978	0.05416
1980	0.06602
1981	0.08422
1982	0.23658
1983	0.19408
1984	0.09369
1985	0.60614
1986	1.09843
1987	0.37247
1988	0.36859
1989	0.29956
1990	0.40566
1991	0.4885
1992	0.393
1993	0.37367
1994	0.5685
1995	0.69561
1996	0.82817
1997	0.79126
1998	1.12769
1999	0.81756
2000	0.86215
2001	0.51468
2002	0.56438
2003	0.73749
2004	0.94075
2005	0.92748
2006	1.26204
2007	1.96622
2008	1.95891
2009	1.93317
2010	2.58382
2011	2.47032
2012	2.50506
2013	2.17216
2014	1.98672
2015	1.71833
2016	2.11768
2017	2.0693