Year	Percent
2003	20.2
2004	18.3
2005	18.3
2006	19.4
2007	19.5
2008	19.7
2009	15.8
2010	17.5
2011	17.5
2012	18.6
2013	21.8
2014	21.6
2015	21.7
2016	21
2017	21.9
2018	21.7
2019	20.7
2020	20.6
2021	22.8