Year	%
1980	46.6
1986	48.5
1987	50.6
1991	52.5
1992	50.9
1993	49.9
1994	51
1995	53.8
1996	54
1997	53.7
1998	55.1
1999	54.2
2000	55.1
2001	57
2002	57.8
2003	55
2004	52.6
2005	52.1
2006	50.7
2007	50.7
2008	49.5
2009	48.4
2010	48.6
2011	47.9
2012	46.6
2013	46.2
2014	47
2016	47.5
2017	46.7
2018	46.9
2019	48.3
2020	47.7
2021	47.8
2022	46.6