Year	Years
1990	77.7
1991	78.4
1992	78.4
1993	78
1994	77.3
1995	76.7
1996	76.4
1997	76.4
1998	76.6
1999	77
2000	77.5
2001	78
2002	78.3
2003	78.5
2004	78.4
2005	78.2
2006	78
2007	78
2008	78.2
2009	78.6
2010	79.1
2011	79.7
2012	80.1
2013	80.3