Year	Percent
1979	3.88
1980	3.84
1981	3.79
1982	4.92
1983	7.18
1984	6.43
1985	5.92
1986	5.84
1987	5.96
1988	5.26
1989	4.59
1990	5.09
1991	7.31
1992	8.28
1993	8.62
1994	7.63
1995	6.63
1996	6.61
1997	6.56
1998	6.1
1999	5.46
2000	5.04
2001	5.3
2002	5.04
2003	4.71
2004	4.14
2005	3.86
2006	3.69
2007	3.39
2008	3.36
2009	4.54
2010	4.04
2011	3.94
2012	4.05
2013	4.56
2014	4.84
2015	4.87
2016	4.5
2017	4.41
2018	4.12
2019	4
2020	5.17