Year	%
2000	30.3
2001	29.9
2002	29.3
2003	29
2004	28.9
2005	28.9
2006	28.1
2007	26.3
2008	25.1
2009	24.6
2010	24.1
2011	23.9
2012	23.1
2013	22.8
2014	22.3
2015	21.9
2016	22
2017	21.3
2018	21.1
2019	21.2