Year	Percent
1979	4.98
1980	3.84
1981	3.81
1982	4.22
1984	3.85
1986	4.24
1987	4.42
1988	3.76
1989	2.15
1990	2.03
1991	5.15
1992	9.58
1993	14.05
1994	14.1
1995	13.97
1996	11.94
1997	12.23
1998	9.9
1999	8.51
2000	7.94
2001	7.25
2002	7.38
2003	7.47
2004	7.44
2005	6.81
2006	6.11
2007	5.33
2008	4.87
2009	6.6
2010	6.8
2011	6.15
2012	6.12
2013	6.59
2014	7.11
2015	7.71
2016	7.41
2017	7.08
2018	6.04
2019	5.08
2020	5.83