Year	%
1981	14.6
1989	14.9
1992	15
1995	15.2
1996	15.2
1997	15.1
1998	14.9
2000	14.7
2001	13.9
2002	13.8
2003	13.8
2004	13.7
2005	14.1
2006	13.5
2007	13.4
2008	13.8
2009	13.8
2010	14
2011	14.7
2012	15.4
2013	15.3
2014	15.4
2015	15.4
2016	15.4
2017	15.4
2018	15.3
2019	15.4
2020	15.3
2021	15.1
2022	15.2