Year	Years
1990	61.2
1991	61.2
1992	61
1993	60.5
1994	59.6
1995	58.5
1996	57.2
1997	55.6
1998	53.6
1999	51.6
2000	49.8
2001	48.3
2002	47
2003	45.8
2004	44.8
2005	44.1
2006	44
2007	44.4
2008	45.2
2009	46.3
2010	47.4
2011	48.3
2012	48.2
2013	48.3