Year	%
1968	4.5
1969	5.2
1970	4.7
1971	6.5
1972	7.2
1973	5.5
1974	6.5
1975	6.2
1976	6
1977	6
1978	7
1979	6
1980	7
1981	8.2
1982	8.5
1983	8.5
1984	8.7
1985	9.2
1986	10.2
1987	10.7
1988	10.2
1989	11.2
1990	12
1991	12.2
1992	13.2
1993	13.7
1994	12.7
1995	12.5
1996	12.7
1997	13.2
1998	13
1999	13.2
2000	12.5
2001	12.2
2002	12
2003	12.2
2004	11.7
2005	12.7
2006	12.5
2007	13
2008	12.7
2009	12
2010	11.2
2011	11.5
2012	11.2
2013	11.2
2014	12
2015	12
2016	12.2
2017	12.5
2018	12.2
2019	13
2020	11.5
2021	11.7