Year	Percent
1983	8.5
1985	8.1
1986	6.8
1987	4.4
1988	4
1989	3.7
1990	3.9
1991	3.6
1992	4
1993	4.5
1994	4.1
1995	3.7
1996	4.4
1997	5
1998	5.1
1999	5.3
2000	6.32
2001	7.11
2002	6.9
2003	7.49
2004	7.32
2005	6.92
2006	6.8
2007	6.47
2008	5.98
2009	6.89
2010	6.85
2011	6.38
2012	6.2
2013	6.11
2014	5.72
2015	5.38
2016	4.69
2017	4
2018	3.66
2019	3.62
2020	4.26