Year	Percent
1980	11.46
1981	10.16
1982	10.08
1983	9.17
1984	8.85
1985	10.04
1986	8.99
1987	7.67
1988	7.2
1989	6.78
1990	6.98
1991	7.31
1992	7.64
1993	8.95
1994	7.24
1995	6.27
1996	6.1
1997	7.58
1998	15.86
1999	14.02
2000	10.21
2001	9.56
2002	8.1
2003	9.67
2004	10.09
2005	9.56
2006	9.13
2007	8.01
2008	8.82
2009	9.37
2010	8.66
2011	8.42
2012	7.85
2013	8.04
2014	8.72
2015	10.04
2016	10.29
2017	9.92
2018	10.25
2019	9.95
2020	10.26