Year	%
1991	14
1995	13.28
1996	14.05
1997	14.16
1998	14.07
1999	17.33
2000	17.3
2001	17.28
2002	17.4
2003	17.44
2004	16.7
2005	13.77
2006	13.65
2007	11.55
2008	11.41
2009	10.26
2010	7.56
2011	6.53
2012	6.02
2013	5.78
2014	5.75
2015	5.64
2016	5.7
2017	5.86
2018	5.67