Year	Percent
1978	0.7042
1979	0.6757
1980	0.6637
1981	0.2101
1982	0.8048
1983	1.1583
1984	1.1194
1985	1.2704
1986	1.087
1987	0.7055
1988	0.5217
1989	0.5172
1990	0.3565
1991	0.5367
1992	0.3591
1993	0.5445
1994	0.5515
1995	0.5525
1996	1.1257
1997	1.4925
1998	1.3233
1999	1.3672
2000	1.6097
2001	2.5
2002	2.9106
2003	3.5343
2004	2.988
2005	2.8571
2006	2.1583
2007	1.9967
2008	2.3328
2009	3.7258
2010	3.1812
2011	2.682
2012	2.5271
2013	2.1965
2014	1.9846
2015	1.6967
2016	2.0576
2017	1.9211