Year	%
1980	40.8
1986	42.8
1987	45.3
1991	46.8
1992	45.5
1993	44.9
1994	45.9
1995	48.9
1996	49.5
1997	49.1
1998	50.7
1999	49.8
2000	51.1
2001	53.3
2002	53.8
2003	51
2004	48.5
2005	47.8
2006	46.4
2007	46.3
2008	45
2009	43.8
2010	43.7
2011	42.7
2012	41.4
2013	41.1
2014	41.8
2016	42.3
2017	41.4
2018	41.7
2019	43.3
2020	42.7
2021	42.4
2022	40.7