Year	Percent
1983	8.13
1984	7.93
1985	8.67
1986	8.81
1987	9.67
1988	9.03
1989	7.71
1990	7.33
1991	7.75
1992	8.15
1993	10.02
1994	9.13
1995	7.63
1996	7.09
1997	6.34
1998	5.36
1999	5.13
2000	4.49
2001	3.27
2002	3.46
2003	3.32
2004	3.09
2005	2.75
2006	3.01
2007	3.21
2008	3.14
2009	4.59
2010	4.74
2011	5.01
2012	4.94
2013	4.82
2014	4.04
2015	3.45
2016	3.69
2017	3.54
2018	3.25
2019	2.95