Year	%
2000	30.7
2001	30.2
2002	30
2003	29.9
2004	29.2
2005	29.4
2006	30.1
2007	30.4
2008	30.5
2009	30.1
2010	29.5
2011	29.8
2012	31.2
2013	25.7
2014	22.6
2015	22.2
2016	21.5
2017	21
2018	20.4
2019	20.3