Year	%
1998	24.9
1999	24
2000	24
2001	24
2002	24
2003	22.6
2004	21.4
2005	21.8
2006	22.4
2007	23.6
2008	22.3
2009	22.6
2010	22.9
2011	21.9
2012	21.8
2013	22.1
2014	22.6
2015	21.2
2016	21.3
2017	21.3
2018	21.4
2019	21.3
2020	20.7