Year	%
1987	22.5
1992	22.6
1995	22.5
2000	22.6
2003	22.5
2004	22.6
2005	22.5
2006	22.3
2007	22.1
2008	22.5
2009	22.5
2010	22.3
2011	22.3
2012	22.1
2013	21.9
2014	22
2015	21.8
2016	22
2017	21.9
2018	21.9
2019	21.9
2020	22.1
2021	21.8