Year	Percent
1977	0.46
1978	0.54
1979	0.39
1980	0.84
1981	1.35
1983	0.93
1984	0.72
1985	1.79
1986	2.85
1987	1.75
1988	1.48
1989	1.56
1990	1.23
1991	1.61
1992	3.98
1993	2.46
1994	2.35
1995	1.97
1996	1.41
1997	1.62
1998	1.52
1999	1.07
2000	1.71
2002	1.59
2003	2.04
2004	1.85
2005	2.32
2006	1.71
2007	1.42
2008	2.49
2009	2.78
2010	2.52
2011	2.06
2012	4
2013	6.35
2014	5.2
2015	4.09
2016	4.41
2017	4.07
2018	4.46
2019	5.48
2020	5.33