Year	Years
1990	49.5
1991	49.1
1992	48.7
1993	48.3
1994	47.8
1995	47.3
1996	46.9
1997	46.5
1998	46.2
1999	46.2
2000	46.3
2001	46.6
2002	47
2003	47.4
2004	47.8
2005	48.4
2006	49.3
2007	50.3
2008	51.4
2009	52.6
2010	53.8
2011	54.8
2012	55.9
2013	57.3