Year	Percent
1980	2.19
1981	2
1982	1.42
1983	1.37
1984	1.4
1985	1.34
1986	1.21
1987	1.02
1988	0.83
1989	0.82
1990	0.81
1991	0.62
1992	0.69
1993	0.67
1994	0.63
1995	0.87
1996	0.66
1997	1.06
1998	4.06
1999	4.5
2000	2.62
2001	2.07
2002	1.63
2003	1.91
2004	2.1
2005	2.3
2006	2.16
2007	1.99
2008	1.77
2009	2.17
2010	2.51
2011	2.11
2012	2.06
2013	1.87
2014	2.18
2015	2.79
2016	2.69
2017	2.4
2018	2.87
2019	2.93
2020	3.17