Year	Years
1990	55.7
1991	55.7
1992	55.8
1993	56
1994	56.2
1995	56.3
1996	56.5
1997	56.6
1998	56.2
1999	56.8
2000	56.9
2001	56.9
2002	57
2003	57.1
2004	57.2
2005	57.3
2006	57.5
2007	57.8
2008	58.2
2009	58.4
2010	58.7
2011	59.1
2012	59.4
2013	59.8