Year	Years
1970	1.41
1971	1.45
1972	1.5
1973	1.55
1974	1.6
1975	1.65
1976	1.71
1977	1.76
1978	1.82
1979	1.88
1980	1.94
1981	2
1982	2.06
1983	2.12
1984	2.19
1985	2.26
1986	2.33
1987	2.4
1988	2.48
1989	2.55
1990	2.63
1991	2.71
1992	2.79
1993	2.88
1994	2.96
1995	3.05
1996	3.14
1997	3.23
1998	3.33
1999	3.42
2000	3.52
2001	3.62
2002	3.73
2003	3.83
2004	3.94
2005	4.05
2006	4.16
2007	4.27
2008	4.38
2009	4.5
2010	4.62
2011	4.74
2012	4.86
2013	4.98
2014	5.11
2015	5.24