Year	Years
1990	77.4
1991	77.6
1992	77.7
1993	77.8
1994	77.9
1995	78
1996	78.3
1997	78.7
1998	78.9
1999	79.1
2000	79.3
2001	79.5
2002	79.7
2003	79.9
2004	80.1
2005	80.3
2006	80.5
2007	80.6
2008	80.7
2009	80.9
2010	81.1
2011	81.3
2012	81.4
2013	81.5