Year	Years
1970	1.49
1971	1.53
1972	1.57
1973	1.61
1974	1.65
1975	1.7
1976	1.74
1977	1.79
1978	1.83
1979	1.88
1980	1.93
1981	1.98
1982	2.03
1983	2.08
1984	2.14
1985	2.19
1986	2.25
1987	2.3
1988	2.36
1989	2.42
1990	2.48
1991	2.54
1992	2.61
1993	2.67
1994	2.73
1995	2.8
1996	2.86
1997	2.93
1998	2.99
1999	3.06
2000	3.12
2001	3.19
2002	3.26
2003	3.33
2004	3.41
2005	3.48
2006	3.56
2007	3.63
2008	3.71
2009	3.79
2010	3.87
2011	3.95
2012	4.04
2013	4.12
2014	4.21
2015	4.3