Year	%
1980	59.1
1988	53.1
1989	53.6
1991	51.3
1992	51.5
1996	56.9
1999	58.7
2000	58.7
2001	57.5
2002	56
2003	53.6
2004	55
2005	53.9
2008	55.3
2009	54.3
2010	54.6
2011	53.5
2012	52.6
2013	52.6
2014	52.6
2015	51
2016	50.6
2017	49.7
2018	50.4
2019	51.3
2020	53.5
2021	55.1
2022	54.8