Year	%
2000	37.3
2001	36.2
2002	39.1
2003	39.2
2004	39.8
2005	40.2
2006	38.5
2007	38.6
2008	37.9
2009	34.5
2010	33.1
2011	31.1
2012	29.9
2013	29.4
2014	29.4
2015	28.5
2016	28.3
2017	27.4
2018	27.4
2019	27.7