Year	%
2000	30.8
2001	29.6
2002	28.6
2003	27.4
2004	27.3
2005	26.6
2006	26.3
2007	24.7
2008	23.7
2009	23.7
2010	24.5
2011	24.7
2012	24.2
2013	24.1
2014	23.6
2015	22.8
2016	22.5
2017	22.3
2018	21.6
2019	20.6