Year	%
1975	14.5
1981	15.1
1987	15
1992	14.5
1995	14.5
2000	14
2001	14.1
2002	14.2
2003	14.6
2004	14.3
2005	14.4
2006	14.3
2007	14.3
2008	14.1
2009	14.3
2010	14.2
2011	14.3
2012	14.3
2013	14
2014	14
2015	13.9
2016	13.8
2017	13.9
2018	13.7
2019	13.8
2020	13.8
2021	13.7