Year	%
1988	24.75
1989	35.54
1990	23.61
1991	10.45
1992	34.42
1993	17.81
1994	20.58
1995	22.89
1996	18.29
1997	18.2
1998	18.49
1999	18.38
2000	15.96
2001	14.2
2002	14.3
2003	13.99
2004	12.23
2005	12.7
2006	12.3
2007	12.51
2008	12.57
2009	12.31
2010	12.19
2011	12.19
2012	11.6
2013	11.92
2014	11.32
2015	11.72
2016	11.37
2017	10.48