Year	Years
1970	1.82
1971	1.87
1972	1.92
1973	1.96
1974	2.01
1975	2.07
1976	2.12
1977	2.17
1978	2.22
1979	2.28
1980	2.33
1981	2.39
1982	2.45
1983	2.51
1984	2.57
1985	2.63
1986	2.69
1987	2.76
1988	2.83
1989	2.9
1990	2.97
1991	3.05
1992	3.12
1993	3.2
1994	3.29
1995	3.38
1996	3.48
1997	3.59
1998	3.7
1999	3.81
2000	3.93
2001	4.05
2002	4.16
2003	4.29
2004	4.41
2005	4.53
2006	4.66
2007	4.79
2008	4.92
2009	5.05
2010	5.19
2011	5.32
2012	5.46
2013	5.59
2014	5.73
2015	5.87