Year	%
1989	59.5
1990	57.4
1991	51.9
1992	51.8
1993	53.5
1994	55
1995	55.5
1996	55.7
1997	52.7
1998	57.4
1999	55.4
2001	55.4
2002	55.7
2003	58.1
2004	58.1
2005	59.5
2006	57.5
2007	55.8
2008	55.5
2009	51.3
2010	53.1
2011	52.6
2012	53.4
2013	50
2014	49.9
2015	49.2
2016	49.8
2017	49.4
2018	48.9
2019	48.2