Year	%
1991	13
1992	13.3
1993	13.4
1994	13.3
1995	13.6
1996	13.6
1997	13.5
1998	13.5
1999	13.4
2000	13.5
2001	13.2
2002	13.2
2003	13.3
2004	13.1
2005	12.8
2006	12.9
2007	12.9
2008	12.9
2009	13
2010	13.1
2011	13
2012	12.9
2013	12.8
2014	13
2015	12.9
2016	12.9
2017	13.1
2018	12.9
2019	13