Year	Percent
1991	12.3
1995	13.1
1996	12.8
1998	12.6
1999	12.9
2000	12.7
2001	12.8
2002	12.7
2003	13.4
2004	13.6
2005	13.3
2006	13.8
2007	13.7
2008	13.3
2009	13.8
2010	14.4
2011	14.5
2012	14.7
2013	14.3
2014	14.7
2015	14.8
2016	15.2