Year	%
2000	42.3
2001	41.8
2002	41.4
2003	41.1
2004	40.7
2005	40.2
2006	39.9
2007	39.2
2008	38.3
2009	37.5
2010	36.5
2011	35.3
2012	33.9
2013	32.3
2014	31.1
2015	29.9
2016	28.9
2017	27.7
2018	26.6
2019	25.5