Year	%
1981	9
1988	9.4
1990	9.1
1992	8.5
1994	9.6
1996	9.8
1998	9.9
1999	9.6
2000	9.6
2002	9.9
2004	9.7
2006	9.9
2007	10.3
2008	10.1
2009	10.3
2010	10.4
2011	11.1
2012	10.4
2013	10.8
2014	11
2015	11.3
2016	11.1
2017	11.1
2018	11.1
2019	11.5
2020	11.5
2021	11.5