Year	Percent
1980	0.664
1981	0.31
1982	0.28
1983	0.289
1984	0.306
1985	0.283
1986	0.271
1987	0.254
1988	0.24
1989	0.275
1990	0.254
1991	0.131
1992	0.249
1993	0.245
1994	0.23
1995	0.437
1996	0.32
1997	0.408
1998	1.998
1999	2.152
2000	1.6478
2001	1.0341
2002	0.9184
2003	1.3253
2004	1.478
2005	1.6192
2006	1.2641
2007	1.3225
2008	1.0503
2009	1.6597
2010	2.1877
2011	1.6965
2012	1.7212
2013	1.2197
2014	1.8638
2015	1.9847
2016	2.1111
2017	1.9323