Year	Percent
1977	2.03422
1978	1.37942
1979	1.07793
1980	1.0887
1981	2.65263
1982	1.10871
1983	1.52649
1984	1.21683
1985	1.45727
1986	1.11357
1987	1.37473
1988	2.01525
1989	1.4753
1990	2.19492
1991	2.48849
1992	2.64991
1993	2.58669
1994	2.85259
1995	2.92614
1996	3.67481
1997	3.25181
1998	4.50218
1999	4.3638
2000	4.83913
2001	3.9077
2002	4.38159
2003	4.50333
2004	5.84853
2005	7.66227
2006	7.96889
2007	8.38133
2008	7.95779
2009	5.28302
2010	5.1167
2011	6.46733
2012	5.80184
2013	6.44362
2014	6.41023
2015	5.39565
2016	4.59814
2017	5.0055