Year	%
1977	13.2
1978	12
1979	12.7
1980	10.5
1981	10.2
1982	9.7
1983	10.4
1984	11.7
1986	10
1987	14
1989	11.5
1991	10.5
1993	16
1995	15.7
1998	15.7
2000	15.2
2002	15.2
2003	13.5
2004	13.3
2005	14.1
2006	13.4
2007	13.2
2008	13.4
2009	13.7
2010	14.5
2011	14.7
2012	14.2
2013	14.8
2014	15.2
2015	16.1
2016	15.7
2017	16
2018	15.2
2019	15
2020	15.6
2021	15.3