Year	%
1980	16.6
1985	16.4
1990	17
1993	16.5
1994	16.8
1995	16.5
1996	16.6
1997	16.7
1998	16.7
1999	16.7
2000	16.8
2003	17.5
2004	17.1
2005	17.4
2006	17.2
2007	16.9
2008	17
2009	16.9
2010	16.8
2011	16.9
2012	17
2013	17
2014	17
2015	17
2016	17.1
2017	17.2
2018	17.1
2019	17.3
2020	17.2
2021	17.2