Year	%
1985	20.6
1988	21.1
1992	20.1
1995	22.8
1997	21.6
2000	28.3
2003	22.2
2004	25.1
2005	23.9
2006	22.4
2007	23.5
2008	22.7
2009	22.7
2010	22.7
2011	22.4
2012	21.9
2013	21.8
2014	22.4
2015	22.2
2016	22.2
2017	21.9
2018	22.2
2019	22.3
2020	21.4
2021	21.9