Year	Years
1990	77
1991	77.2
1992	77.3
1993	77.3
1994	77.5
1995	77.6
1996	77.7
1997	78
1998	78
1999	78.1
2000	78.1
2001	78.3
2002	78.5
2003	78.7
2004	79.1
2005	79.5
2006	79.9
2007	80.1
2008	80.3
2009	80.4
2010	80.5
2011	80.6
2012	80.6
2013	80.6