Year	Percent
1998	8.9
2000	12.7
2001	12.8
2002	12.9
2003	13.3
2004	11.6
2005	12.3
2006	10.9
2007	12
2008	12.6
2009	13
2010	13.3
2011	13.5
2012	13.9
2013	13.3
2014	13.8
2015	13.4
2016	13.9