Year	Percent
1979	5.13
1980	5.37
1981	5.78
1982	5.73
1984	6.55
1986	6.36
1987	4.52
1988	4.65
1989	3.74
1990	2.25
1991	5.07
1992	10.85
1993	15.71
1994	18.96
1995	13.12
1996	14.78
1997	12.79
1998	13.32
1999	10.44
2000	9.38
2001	8.97
2002	7.51
2003	8.25
2004	8.35
2005	6.88
2006	6.77
2007	6.35
2008	5.39
2009	6.23
2010	6.52
2011	6.42
2012	6.58
2013	6.95
2014	7.27
2015	8.02
2016	7.52
2017	7.82
2018	6.9
2019	6.59
2020	7.45