Year	%
1988	13.11
1989	16.21
1990	13.85
1991	19.23
1992	15.67
1993	19.46
1994	19.31
1995	10.24
1996	8.02
1997	8.19
1998	7.12
1999	9.3
2000	7.25
2001	7.18
2002	6.3
2003	6.7
2004	6.51
2005	5.98
2006	6.02
2007	5.92
2008	5.91
2009	5.68
2010	5.57
2011	5.64
2012	4.96
2013	5.33
2014	4.44
2015	4.87
2016	5.16
2017	4.53