Year	%
1988	14.19
1989	32.95
1990	15.49
1991	17.26
1992	26.44
1993	19.81
1994	20.44
1995	12.16
1996	13.25
1997	11.71
1998	12.37
1999	13.91
2000	11.96
2001	11.56
2002	9.68
2003	8.71
2004	7.59
2005	6.96
2006	6.28
2007	6.81
2008	6.68
2009	5.87
2010	5.97
2011	6.81
2012	6.96
2013	6.39
2014	5.99
2015	6.04
2016	5.08
2017	5.53