Year	%
1980	47.4
1988	41.2
1989	42.3
1991	39.5
1992	40.5
1996	45.6
1999	46.9
2000	47
2001	46.3
2002	45.2
2003	42.8
2004	44.5
2005	43.2
2008	43.7
2009	42.9
2010	43.4
2011	42.4
2012	41.3
2013	41.4
2014	41.4
2015	39.9
2016	39.8
2017	39
2018	39.7
2019	40.3
2020	41.8
2021	43.7
2022	43.5