Year	Percent
1981	0.26
1982	0.61
1983	0.39
1984	0.67
1985	0.55
1986	0.45
1987	0.44
1988	0.68
1989	0.54
1990	0.88
1991	1.14
1992	0.91
1993	0.81
1994	0.62
1995	0.76
1996	1.11
1997	0.9
1999	1.4
2000	1.04
2002	0.75
2003	1.1
2006	1.2
2007	1.12
2008	0.83
2010	1.34
2011	2.57
2012	4.44
2013	9.07
2014	10.76
2015	10.04
2016	12.77
2017	11.66
2018	10.57
2019	9.76
2020	8.63