Year	%
1981	21.6
1989	21.8
1992	22
1995	22.3
1996	22.3
1997	22.1
1998	22.1
2000	21.9
2001	21.8
2002	21.7
2003	21.4
2004	21.5
2005	21.7
2006	21.2
2007	21.1
2008	21.4
2009	21.5
2010	21.6
2011	22.1
2012	22.8
2013	22.4
2014	22.5
2015	22.6
2016	22.5
2017	22.4
2018	22.5
2019	22.5
2020	22.5
2021	22.2
2022	22.1