Year	Years
1990	60.5
1991	60.3
1992	60.2
1993	60.1
1994	59.9
1995	59.7
1996	59.4
1997	59.2
1998	58.9
1999	58.5
2000	58
2001	57.5
2002	57.2
2003	56.9
2004	56.7
2005	57
2006	57.6
2007	57.7
2008	57.5
2009	57.3
2010	57.5
2011	57.8
2012	58.4
2013	59.1