Year	%
1980	19.3
1986	17.9
1987	18.7
1991	17.2
1992	19.6
1993	20.1
1994	20.7
1995	21.2
1996	22.5
1997	24.3
1998	23
1999	22.8
2000	24.5
2001	26.1
2002	25.9
2003	24.5
2004	24
2005	23.5
2006	22.9
2007	23.1
2008	21.8
2009	22.1
2010	21.6
2011	20.7
2012	20.1
2013	19.9
2014	19.9
2016	20.2
2017	18.9
2018	19.2
2019	20.3
2020	20.1
2021	18.2
2022	18.3