Year	Percent
1983	20.22
1984	19.1
1985	18.25
1986	18.52
1987	16.21
1988	13.24
1989	10.34
1990	10.42
1991	13.88
1992	15.68
1993	17.48
1994	16.36
1995	15.55
1996	14.94
1997	13.6
1998	12.46
1999	12.42
2000	12.03
2001	10.33
2002	10.92
2003	11.36
2004	10.72
2005	12.74
2006	13.93
2007	14.28
2008	15.02
2009	19.12
2010	19.88
2011	21.29
2012	21.21
2013	20.68
2014	16.95
2015	14.63
2016	13.01
2017	12.11
2018	11.3
2019	11.16