Year	%
1992	19.6
1993	23.6
1996	22.1
2002	22.5
2004	23.1
2005	22.9
2006	22.6
2007	22.3
2008	22.9
2009	22.4
2010	22.4
2011	22.2
2012	22.2
2013	22.6
2014	22.1
2015	22.1
2016	21.9
2017	21.5
2018	21.5
2019	21.5
2020	22.5
2021	22.2