Year	Years
1970	1.82
1971	1.87
1972	1.92
1973	1.97
1974	2.02
1975	2.07
1976	2.12
1977	2.17
1978	2.23
1979	2.28
1980	2.34
1981	2.4
1982	2.46
1983	2.52
1984	2.58
1985	2.64
1986	2.71
1987	2.78
1988	2.84
1989	2.91
1990	2.98
1991	3.05
1992	3.13
1993	3.2
1994	3.28
1995	3.36
1996	3.44
1997	3.52
1998	3.6
1999	3.69
2000	3.78
2001	3.86
2002	3.95
2003	4.05
2004	4.14
2005	4.23
2006	4.33
2007	4.43
2008	4.53
2009	4.63
2010	4.73
2011	4.84
2012	4.94
2013	5.05
2014	5.16
2015	5.27