Year	Percent
1975	3.1
1976	3.5
1977	3.7
1978	3.1
1979	2.3
1980	2.9
1981	4.6
1982	5.9
1983	7.1
1984	7.4
1985	8
1986	7.7
1987	5.8
1988	3.3
1989	2
1990	2.1
1991	4.1
1992	4.3
1993	4.9
1994	4.7
1995	4.4
1996	3.54
1999	0.8
2000	0.6
2001	1.6
2002	0.5
2003	0.8
2004	1
2005	1.4
2006	2.42
2007	1.4
2008	1.4
2011	3.3
2013	2.6
2014	1.98
2016	2.67