Year	Years
1970	67.02
1971	67.15
1972	67.49
1973	67.87
1974	68.23
1975	68.38
1976	68.55
1977	68.76
1978	68.96
1979	69.09
1980	69.19
1981	69.08
1982	69.22
1983	69.4
1984	69.48
1985	69.48
1986	69.46
1987	69.77
1988	69.96
1989	69.82
1990	69.84
1991	69.91
1992	69.83
1993	69.84
1994	70.25
1995	71.26
1996	71.33
1997	72.24
1998	72.63
1999	72.77
2000	72.6
2001	73.56
2002	73.87
2003	74.17
2004	74.76
2005	75.23
2006	75.4
2007	75.86
2008	76.28
2009	76.66
2010	77.05
2011	77.5
2012	77.89
2013	78.24
2014	78.5
2015	78.97
2016	79.06