Year	%
1991	11.91
1995	11.35
1996	14.02
1997	13.08
1998	13.05
1999	15.78
2000	15.15
2001	15.24
2002	15.57
2003	15.44
2004	13.85
2005	12.75
2006	11.78
2007	11.42
2008	10.83
2009	8.26
2010	5.64
2011	5.37
2012	5.17
2013	4.87
2014	4.64
2015	4.45
2016	4.35
2017	4.32
2018	3.92