Year	%
1988	13.5
1989	24.95
1990	22.63
1991	15.61
1992	16.42
1993	16.46
1994	19.33
1995	15.36
1996	12.43
1997	12.26
1998	12.66
1999	13.13
2000	12.7
2001	11.44
2002	11.74
2003	10.85
2004	10.28
2005	10.53
2006	10.12
2007	9.82
2008	9.88
2009	9.79
2010	9.67
2011	9.67
2012	9.22
2013	9.36
2014	9.14
2015	9.33
2016	9.25
2017	8.9