Year	%
1992	17.7
1993	17.3
1995	15.4
1996	16.2
2002	17.3
2003	17.2
2004	17.3
2005	17.2
2006	17
2007	17.6
2008	17.6
2009	17.8
2010	17.9
2011	18
2012	17.9
2013	17.9
2014	18
2015	17.8
2016	17.9
2017	17.8
2018	17.8
2019	17.5
2020	17.6