Year	Years
1970	1.2
1971	1.24
1972	1.28
1973	1.32
1974	1.36
1975	1.41
1976	1.45
1977	1.5
1978	1.55
1979	1.6
1980	1.66
1981	1.72
1982	1.78
1983	1.84
1984	1.9
1985	1.97
1986	2.04
1987	2.11
1988	2.19
1989	2.27
1990	2.35
1991	2.44
1992	2.53
1993	2.63
1994	2.73
1995	2.83
1996	2.94
1997	3.05
1998	3.15
1999	3.26
2000	3.36
2001	3.47
2002	3.58
2003	3.69
2004	3.79
2005	3.9
2006	4.01
2007	4.12
2008	4.23
2009	4.33
2010	4.44
2011	4.55
2012	4.65
2013	4.76
2014	4.87
2015	4.97