Year	Years
1970	1.78
1971	1.83
1972	1.88
1973	1.93
1974	1.98
1975	2.04
1976	2.09
1977	2.15
1978	2.21
1979	2.27
1980	2.33
1981	2.4
1982	2.46
1983	2.53
1984	2.6
1985	2.67
1986	2.74
1987	2.82
1988	2.89
1989	2.97
1990	3.05
1991	3.14
1992	3.22
1993	3.31
1994	3.4
1995	3.49
1996	3.59
1997	3.68
1998	3.78
1999	3.88
2000	3.98
2001	4.07
2002	4.17
2003	4.28
2004	4.38
2005	4.48
2006	4.58
2007	4.69
2008	4.79
2009	4.9
2010	5.01
2011	5.12
2012	5.23
2013	5.34
2014	5.45
2015	5.56