Year	%
1996	42.3
2001	42.9
2002	42.3
2003	41.3
2004	40.2
2005	46.1
2006	39.5
2007	39.3
2008	38.1
2009	37.7
2010	37.7
2011	37.6
2012	37.7
2013	37
2014	37
2015	36.9
2016	37.2
2017	37.4
2018	37.9
2019	38.1
2020	38.8
2021	39.3