Year	Years
1990	80.7
1991	80.8
1992	81
1993	81.2
1994	81.4
1995	81.6
1996	81.8
1997	82.1
1998	82.3
1999	82.5
2000	82.7
2001	82.9
2002	83
2003	83.1
2004	83
2005	83.1
2006	83.2
2007	83.4
2008	83.5
2009	83.6
2010	83.7
2011	83.8
2012	83.8
2013	83.9