Year	%
1988	19.97
1989	27.83
1990	16.47
1991	11.33
1992	28.13
1993	15.51
1994	23.41
1995	30.57
1996	19.42
1997	18.88
1998	20.33
1999	18.63
2000	15.7
2001	14.93
2002	14.44
2003	13.53
2004	12.86
2005	12.27
2006	11.89
2007	11.97
2008	11.83
2009	11.51
2010	11.61
2011	11.46
2012	11.5
2013	10.76
2014	10.39
2015	10.39
2016	9.99
2017	7.76