Year	%
1987	42.7
1994	44.4
1995	44.5
1996	43.2
2000	41
2002	40.2
2003	40.8
2004	41.4
2005	41.8
2006	40.7
2007	40.3
2008	39.3
2009	40.7
2010	40.2
2011	40.7
2012	41.1
2013	41.3
2014	40.1
2015	40.2
2016	41.2
2017	40
2018	39.7
2019	39.7
2020	38.3
2021	39.2