Year	Years
1990	51.7
1991	50.9
1992	50.2
1993	49.6
1994	49.1
1995	48.8
1996	48.6
1997	48.6
1998	49
1999	49.4
2000	50
2001	50.8
2002	51.5
2003	52.4
2004	53.3
2005	54.5
2006	55.9
2007	56.6
2008	57.2
2009	57.9
2010	58.4
2011	58.8
2012	59.3
2013	59.8