Year	Percent
1983	13.53
1984	14.97
1985	16.68
1986	16.44
1987	16.47
1988	16
1989	15.31
1990	13.22
1991	14.64
1992	14.01
1993	14.16
1994	13.25
1995	10.92
1996	10.88
1997	9.39
1998	7.19
1999	5.38
2000	4.05
2001	3.28
2002	3.7
2003	4.01
2004	4.01
2005	3.67
2006	3.85
2007	4.26
2008	5.66
2009	11.02
2010	13.04
2011	14.06
2012	13.96
2013	12.37
2014	10.67
2015	8.88
2016	7.51
2017	5.84
2018	4.83
2019	4.13
2020	4.61