Year	%
1984	16.1
1987	16.2
1990	16
1993	15.7
1996	15.2
1998	16
1999	16
2000	16.6
2001	16.4
2002	15.8
2003	15.7
2004	15.8
2005	15.7
2006	15.5
2007	15.1
2008	15.3
2009	15.2
2010	15.1
2011	14.2
2012	14.1
2013	13.9
2014	14.2
2015	14.3
2016	14.8
2017	15
2018	15
2019	15.2
2020	15.2
2021	15.1
2022	15
2023	14.8