Year	Percent
1977	9.67
1979	10.38
1983	21.05
1985	17.63
1987	16.78
1988	14.24
1989	13.13
1990	11.09
1991	11.1
1992	8.13
1993	10.43
1994	11.32
1995	12.11
1996	11.44
1997	9.75
1998	8.76
1999	7.38
2000	5.26
2001	4.37
2002	4.58
2003	6.58
2004	8
2005	11.85
2006	10.02
2007	9.36
2008	8.58
2009	10.19
2010	11.07
2011	10
2012	11.71
2013	13.17
2014	12.73
2015	11.25
2016	10.82
2017	8.86
2018	7.16
2019	6.73
2020	9.11