Year	%
1977	16.5
1978	16.8
1979	17
1980	16.8
1981	16.9
1982	17.5
1983	17.5
1984	17.1
1986	17.2
1987	16.8
1989	17
1991	17.3
1993	17.2
1995	17
1998	16.8
2000	16.9
2002	17
2003	16.8
2004	16.9
2005	17.1
2006	17
2007	17.2
2008	17.1
2009	17.1
2010	17
2011	16.9
2012	16.9
2013	17
2014	17.2
2015	17.2
2016	17.1
2017	16.9
2018	17
2019	17.1
2020	16.9
2021	16.9