Year	%
2000	32.4
2001	32.3
2002	31
2003	30.5
2004	30.9
2005	29.8
2006	27.4
2007	25.7
2008	27.7
2009	25
2010	25.3
2011	25
2012	23.3
2013	23.9
2014	23.3
2015	22.7
2016	22.2
2017	21.5
2018	20.8
2019	20.3