Year	%
1988	16.41
1989	24.69
1990	14.11
1991	11.32
1992	25.32
1993	12.48
1994	18.2
1995	45.34
1996	12.85
1997	10.22
1998	17.21
1999	9.76
2000	9.83
2001	10.52
2002	10.91
2003	10.59
2004	7.79
2005	8.37
2006	8.55
2007	7.99
2008	8.06
2009	8.89
2010	9.12
2011	8.55
2012	8.18
2013	8.42
2014	8.47
2015	8.66
2016	9.15
2017	7.85