Year	Percent
1976	2.3568
1977	2.4356
1978	1.7291
1979	1.8827
1980	1.8543
1981	1.9274
1982	2.7324
1983	2.3227
1984	2.4487
1985	2.3229
1986	2.5227
1987	2.3305
1988	1.9077
1989	2.0205
1990	1.6275
1991	3.4837
1992	4.4118
1993	5.5554
1994	4.6718
1995	3.8571
1996	3.6161
1997	2.9741
1998	2.6983
1999	3.0224
2000	2.5343
2001	2.8961
2002	3.05
2003	3.5281
2004	3.1372
2005	3.2151
2006	4.6029
2007	3.6523
2008	2.7745
2009	4.8185
2010	5.0384
2011	4.9115
2012	4.7192
2013	4.7361
2014	4.7828
2015	4.8486
2016	5.455
2017	5.4083