Year	%
1981	24.6
1982	25
1983	25.1
1984	24
1985	24.5
1986	24.5
1987	25.7
1988	26.5
1989	26.5
1990	25.9
1992	25.3
1993	25.2
1995	25.6
1996	26.2
1997	25.3
1998	25
1999	25.2
2001	25.9
2002	25.3
2003	25.3
2004	24.5
2005	24.3
2006	23.6
2007	24.2
2008	23.5
2009	23.4
2011	23.1
2012	22.8
2013	22.5
2014	22.2
2015	22.5
2016	23
2017	23.1
2018	23.5
2019	24
2020	18.2
2021	22.2
2022	22