Year	%
1997	53.3
1998	55.1
1999	54.8
2000	49.1
2001	51.3
2002	53.6
2003	53.1
2004	49.9
2005	50.5
2006	50.3
2007	50
2008	47.5
2009	47
2010	45.5
2011	44.7
2012	44.4
2013	43.9
2014	43.1
2015	43.4
2016	43.6
2017	43.3
2018	42.4
2019	41.5
2020	43.7
2021	40.1
2022	40.3