Year	%
1988	18.17
1989	44.95
1990	21.82
1991	19.49
1992	23.72
1993	19.39
1994	15.43
1995	15.08
1996	15.2
1997	13.55
1998	13.65
1999	15.13
2000	15.53
2001	11.82
2002	11.49
2003	11.66
2004	10.83
2005	10.5
2006	9.3
2007	10.19
2008	10.28
2009	9.92
2010	9.35
2011	9.71
2012	9.09
2013	9
2014	8.27
2015	9.27
2016	9.29
2017	9.28