Year	%
1970	44.4
1975	43.3
1979	41.7
1984	41
1990	40.2
1996	39.8
1997	39.7
1998	39.6
1999	40.4
2000	40.5
2001	40.5
2002	40
2003	39.8
2004	39.2
2005	38.5
2006	38.3
2007	40.9
2008	41.2
2009	40.8
2010	41.8
2011	41.4
2012	41.3
2013	40.9
2014	40.6
2015	40.9
2016	40.2
2017	40
2018	40.8
2019	39.2
2020	38.8
2021	39.4