Year	%
1980	22.6
1985	22.2
1990	22.7
1993	22.8
1994	23
1995	22.6
1996	23
1997	22.9
1998	23
1999	22.7
2000	22.7
2003	23.2
2004	23.2
2005	23.2
2006	23.2
2007	23.1
2008	23.1
2009	23.2
2010	23.2
2011	23.5
2012	23.4
2013	23.7
2014	23.6
2015	23.5
2016	23.5
2017	23.4
2018	23.5
2019	23.6
2020	23.7
2021	23.6