Year	Years
1990	51.3
1991	51.1
1992	51
1993	50.8
1994	50.4
1995	50
1996	50
1997	50.6
1998	51.1
1999	51.8
2000	52.4
2001	53.3
2002	53.9
2003	54.4
2004	55
2005	55.5
2006	56.1
2007	56.3
2008	56.7
2009	56.9
2010	57.2
2011	57.4
2012	57.9
2013	58.8