Year	%
1982	21.9
1992	22.6
2000	22.6
2002	23.1
2006	22.7
2007	22.5
2008	22.6
2009	22.7
2010	22.6
2011	22.7
2012	22.5
2013	22.5
2014	22.5
2015	22.6
2016	22.5
2017	22.4
2018	22.5
2019	22.3
2020	22.3