Year	Percent
1975	9.09
1976	4.2
1977	4.2
1978	1.95
1979	2.19
1980	2.62
1981	1.49
1982	1.88
1983	2.11
1984	2.04
1985	2.63
1986	2.53
1987	1.75
1988	1.36
1989	1.06
1990	1.3
1991	1.6
1992	1.89
1993	1.94
1994	1.7
1995	2.93
1996	2.39
1997	2.07
1998	4.03
1999	4.82
2000	4.01
2001	3.84
2002	5.9
2003	6.19
2004	5.55
2005	4.42
2006	3.72
2007	3.36
2008	2.97
2009	4.32
2010	3.51
2011	2.79
2012	2.75
2013	2.97
2014	3.01
2015	3.18
2016	3.08
2017	2.77