Year	Percent
1980	3.75
1981	3.33
1982	3.26
1983	3.2
1984	3
1985	3.09
1986	3.12
1987	2.5
1988	1.92
1989	2.08
1990	1.89
1991	1.7
1992	1.81
1993	2.11
1994	1.94
1995	1.56
1996	1.65
1997	2.16
1998	6.36
1999	5.83
2000	3.75
2001	3.44
2002	2.84
2003	3.03
2004	3.08
2005	3.27
2006	3.11
2007	2.99
2008	2.92
2009	3.37
2010	3.23
2011	2.89
2012	2.71
2013	2.71
2014	3
2015	3.32
2016	3.5
2017	3.61
2018	3.72
2019	3.58
2020	3.76