Year	%
1981	14.1
1986	18.1
1989	14.7
1990	14.6
1991	14.4
1992	14.4
1993	14.3
1994	14
1995	14.3
1996	14
1997	14.2
1998	14.1
1999	13.5
2000	13.7
2001	12.4
2002	12.2
2003	13
2004	13.1
2005	13.3
2006	12.8
2007	12.6
2008	12.8
2009	12.3
2010	12.9
2011	12.9
2012	13
2013	12.6
2014	12.8
2015	12.8
2016	12.8
2017	12.8
2018	13
2019	12.8
2020	12.6
2021	12.8
2022	13.1