Year	Years
1970	1.8
1971	1.85
1972	1.89
1973	1.94
1974	2
1975	2.05
1976	2.1
1977	2.16
1978	2.21
1979	2.27
1980	2.33
1981	2.39
1982	2.45
1983	2.51
1984	2.58
1985	2.64
1986	2.71
1987	2.78
1988	2.85
1989	2.92
1990	2.99
1991	3.07
1992	3.15
1993	3.22
1994	3.3
1995	3.39
1996	3.47
1997	3.56
1998	3.64
1999	3.73
2000	3.82
2001	3.91
2002	4
2003	4.1
2004	4.19
2005	4.29
2006	4.38
2007	4.48
2008	4.58
2009	4.69
2010	4.79
2011	4.89
2012	5
2013	5.11
2014	5.22
2015	5.33