Year	Years
1990	51.1
1991	50.9
1992	51.3
1993	51.2
1994	51.3
1995	51.2
1996	52.2
1997	52.1
1998	51.1
1999	50.6
2000	52.2
2001	52.5
2002	52.9
2003	53.3
2004	53.8
2005	54.4
2006	54.9
2007	55.5
2008	55.9
2009	56.1
2010	56.5
2011	56.8
2012	57.3
2013	57.7