Year	%
1979	15.2
1986	15.5
1992	13.7
1997	17.7
2001	18.2
2002	19.7
2003	20.7
2004	22.7
2005	22
2006	22.2
2007	22.5
2008	21.5
2009	23.5
2010	23.2
2011	21.7
2012	22
2013	20.5
2014	21.2
2015	20.7
2016	21.2
2017	20.5
2018	20.5
2019	20.7
2020	20.2
2021	19.5