Year	%
2000	28.7
2001	27.9
2002	27.2
2003	26.5
2004	25.9
2005	25.4
2006	25.1
2007	24.7
2008	24.3
2009	23.9
2010	23.6
2011	23.3
2012	23.1
2013	22.9
2014	22.7
2015	22.7
2016	22.7
2017	22.6
2018	22.6
2019	22.7