Year	%
1991	13.68
1995	13.12
1996	14.7
1997	14.75
1998	14.69
1999	17.89
2000	17.92
2001	17.89
2002	18.05
2003	18.11
2004	17.47
2005	14.45
2006	13.62
2007	12.53
2008	12.47
2009	11.3
2010	8.94
2011	8.15
2012	7.74
2013	7.71
2014	7.39
2015	7.05
2016	6.99
2017	6.88
2018	6.76