Year	%
1997	57.1
1998	59.3
1999	58.9
2000	53.3
2001	55.5
2002	57.7
2003	57.7
2004	54.3
2005	54.7
2006	54.5
2007	54.2
2008	51.8
2009	51.6
2010	50.3
2011	49.5
2012	49.3
2013	48.9
2014	48.3
2015	48.7
2016	48.8
2017	48.4
2018	47.9
2019	47.2
2020	49.1
2021	46.3
2022	46.5