Year	%
1975	10
1981	10
1987	10.3
1992	9.7
1995	9.4
2000	9.5
2001	9.6
2002	9.5
2003	9.3
2004	9.3
2005	8.7
2006	9.2
2007	8.9
2008	8.6
2009	8.6
2010	8.6
2011	8.5
2012	8.5
2013	8.1
2014	8.4
2015	8.2
2016	8.1
2017	8.3
2018	7.7
2019	8.1
2020	8.2
2021	7.8