Year	Percent
1978	3.5941
1979	3.1283
1980	3.0303
1981	3.4737
1982	4.6709
1983	6.0291
1984	5.445
1985	6.631
1986	5.7773
1987	4.878
1988	4.1341
1989	3.9171
1990	4.3902
1991	4.0353
1992	4.2272
1993	4.4715
1994	4.7361
1995	5.1893
1996	6.8085
1997	6.7239
1998	6.4935
1999	6.6667
2000	6.4935
2001	9.5029
2002	10.192
2003	9.8765
2004	9.0323
2005	9.7973
2006	9.2527
2007	10.1289
2008	11.2426
2009	13.5802
2010	12.6582
2011	12.3932
2012	12.5523
2013	13.0064
2014	12.1622
2015	11.6854
2016	12.5285
2017	12.4183