Year	%
1985	18.2
1988	18.1
1992	18.4
1995	17.7
1997	17.9
2000	16.3
2003	17.9
2004	17.1
2005	17.3
2006	17.7
2007	17.4
2008	17.6
2009	17.7
2010	17.8
2011	18
2012	18
2013	18
2014	17.8
2015	18.1
2016	18.1
2017	18.1
2018	18
2019	17.9
2020	18.1
2021	17.9