Year	%
2004	29.9
2005	34.7
2006	28.3
2007	27.9
2008	27.5
2009	27
2010	29.4
2011	29.2
2012	30.8
2013	31.5
2014	30.9
2015	30.4
2016	30.3
2017	30.6
2018	29.6
2019	30
2020	29.7
2021	29.2