Year	Years
1970	1.75
1971	1.8
1972	1.84
1973	1.88
1974	1.93
1975	1.97
1976	2.01
1977	2.06
1978	2.1
1979	2.15
1980	2.2
1981	2.24
1982	2.29
1983	2.33
1984	2.38
1985	2.42
1986	2.46
1987	2.51
1988	2.55
1989	2.59
1990	2.63
1991	2.67
1992	2.71
1993	2.75
1994	2.78
1995	2.81
1996	2.84
1997	2.88
1998	2.91
1999	2.95
2000	3
2001	3.04
2002	3.09
2003	3.14
2004	3.19
2005	3.24
2006	3.3
2007	3.36
2008	3.42
2009	3.48
2010	3.54
2011	3.61
2012	3.68
2013	3.75
2014	3.82
2015	3.89