Year	Years
1990	52.4
1991	51.1
1992	51.9
1993	52.9
1994	52.8
1995	52.9
1996	53
1997	52.8
1998	53.5
1999	53.8
2000	54.3
2001	54.6
2002	55
2003	55.4
2004	55.7
2005	56.2
2006	56.3
2007	56.4
2008	56.7
2009	56.8
2010	56.9
2011	57.1
2012	57.2
2013	57.7