Year	Years
1970	1.07
1971	1.1
1972	1.14
1973	1.18
1974	1.22
1975	1.26
1976	1.31
1977	1.35
1978	1.4
1979	1.45
1980	1.5
1981	1.55
1982	1.61
1983	1.66
1984	1.72
1985	1.78
1986	1.84
1987	1.9
1988	1.97
1989	2.04
1990	2.11
1991	2.18
1992	2.26
1993	2.33
1994	2.42
1995	2.5
1996	2.58
1997	2.67
1998	2.76
1999	2.85
2000	2.94
2001	3.03
2002	3.13
2003	3.22
2004	3.32
2005	3.41
2006	3.51
2007	3.62
2008	3.72
2009	3.82
2010	3.93
2011	4.03
2012	4.14
2013	4.25
2014	4.37
2015	4.48