Year	Years
1970	67.1
1971	67.51
1972	68.01
1973	68.52
1974	68.84
1975	69.14
1976	69.46
1977	69.58
1978	69.7
1979	69.82
1980	69.94
1981	70.07
1982	70.2
1983	70.23
1984	70.25
1985	70.41
1986	70.46
1987	70.71
1988	70.74
1989	70.95
1990	70.97
1991	70.93
1992	70.9
1993	70.99
1994	71.01
1995	71.02
1996	71.04
1997	71.08
1998	71.25
1999	71.46
2000	71.68
2001	71.74
2002	71.72
2003	71.46
2004	71.64
2005	71.74
2006	71.82
2007	71.98
2008	72.24
2009	70.96
2010	72.41
2011	72.22
2012	72.23
2013	72.17
2014	72.22
2015	72.26
2016	72.4