Year	Years
1970	1.39
1971	1.43
1972	1.47
1973	1.5
1974	1.54
1975	1.58
1976	1.62
1977	1.67
1978	1.71
1979	1.75
1980	1.8
1981	1.84
1982	1.89
1983	1.94
1984	1.99
1985	2.04
1986	2.09
1987	2.14
1988	2.19
1989	2.25
1990	2.3
1991	2.36
1992	2.42
1993	2.48
1994	2.54
1995	2.6
1996	2.66
1997	2.73
1998	2.79
1999	2.86
2000	2.93
2001	3
2002	3.07
2003	3.15
2004	3.22
2005	3.3
2006	3.38
2007	3.46
2008	3.54
2009	3.62
2010	3.71
2011	3.79
2012	3.88
2013	3.97
2014	4.06
2015	4.15