Year	%
1986	22.9
1989	21.6
1992	18.9
1996	19.9
1997	21.2
2000	20.8
2001	20.6
2002	21.2
2003	20.3
2004	20.3
2005	20.2
2006	20.7
2007	19.4
2008	18.8
2009	18.9
2010	19.4
2011	17.5
2012	17.4
2013	17.8
2014	17.8
2015	17.6
2016	18.6
2017	14.2
2018	14.2
2019	14.2
2020	13.6
2021	12.9
2022	14.3