Year	Percent
1980	3.151
1981	3.151
1982	2.249
1983	2.174
1984	2.179
1985	2.141
1986	1.952
1987	1.629
1988	1.275
1989	1.23
1990	1.217
1991	0.991
1992	1.013
1993	0.968
1994	0.909
1995	1.177
1996	0.909
1997	1.52
1998	5.514
1999	6.217
2000	3.9051
2001	3.1273
2002	2.3355
2003	2.5983
2004	2.7436
2005	3.1218
2006	3.0718
2007	2.7038
2008	2.5428
2009	2.7915
2010	3.3574
2011	2.9634
2012	2.9883
2013	2.7538
2014	2.9321
2015	3.3265
2016	3.2168
2017	2.8157