Year	%
1979	21.7
1989	20.9
1991	20.8
1995	20.3
1997	19.7
1998	19.8
1999	20.1
2000	19.8
2001	20.3
2002	19.9
2003	20
2004	20.3
2005	20.7
2006	20.4
2007	20.7
2008	20
2009	20.1
2010	20.2
2011	20.3
2012	20.3
2013	20.3
2014	20.7
2015	20.5
2016	21
2017	20.9
2018	21.2
2019	20.7
2021	20.2
2023	21.2