Year	%
1997	20.4
1998	19.1
1999	19.3
2000	21.5
2001	20.7
2002	19.6
2003	19.3
2004	20.8
2005	20.8
2006	21.1
2007	21.1
2008	21.8
2009	21.7
2010	21.8
2011	22
2012	22
2013	22.1
2014	22.2
2015	21.8
2016	22.1
2017	22.2
2018	22.2
2019	22.3
2020	22
2021	22.1
2022	22