Year	Percent
1975	0.3
1976	0.7
1977	0.4
1978	0.4
1979	0.4
1980	0.2
1981	0.2
1982	0.4
1983	0.9
1984	1.1
1985	1
1986	0.8
1987	0.8
1988	0.7
1989	0.6
1990	2.07
1991	1.78
1992	2.81
1993	3.72
1994	3.88
1995	3.33
1996	3.71
1997	4.2
1998	3.6
1999	3.15
2000	2.67
2001	2.49
2002	2.92
2003	4.12
2004	4.32
2005	4.44
2006	4
2007	3.65
2008	3.35
2009	4.12
2010	4.8
2011	4.4
2012	4.48
2013	4.75
2014	4.83
2015	4.8
2016	4.92
2017	4.8
2018	4.71
2019	4.39
2020	4.82