Year	%
1983	22.6
1987	22.4
1990	22.4
1993	23.1
1999	23.1
2004	22.6
2005	22.5
2006	22
2007	22.2
2008	22.4
2009	22.7
2010	22.6
2011	22.5
2012	22.4
2013	22.5
2014	22.4
2015	22.4
2016	22.4
2017	22.3
2018	22.4
2019	22.2
2020	22.5
2021	22.5