Year	%
1971	11.7
1973	12.2
1975	12.4
1977	12.4
1979	12.5
1981	12.5
1982	12.7
1984	12.6
1985	12.7
1986	13
1987	13
1988	13.1
1989	13.1
1990	13.1
1991	12.9
1992	13
1993	13
1994	13
1995	13
1996	12.6
1997	12.5
1998	12.6
1999	12.6
2000	12.5
2001	12.4
2002	12.4
2003	12.4
2004	12.4
2005	12.4
2006	12.2
2007	12.3
2008	12.3
2009	12.2
2010	12.4
2011	12.6
2012	12.4
2013	12.4
2014	12.5
2015	12.4
2016	12.6
2017	12.4
2018	12.6
2019	12.8