Year	Years
1970	1.7
1971	1.74
1972	1.79
1973	1.84
1974	1.88
1975	1.93
1976	1.98
1977	2.04
1978	2.09
1979	2.14
1980	2.2
1981	2.25
1982	2.31
1983	2.37
1984	2.43
1985	2.5
1986	2.56
1987	2.63
1988	2.69
1989	2.76
1990	2.83
1991	2.9
1992	2.98
1993	3.05
1994	3.13
1995	3.21
1996	3.29
1997	3.37
1998	3.45
1999	3.54
2000	3.62
2001	3.71
2002	3.8
2003	3.89
2004	3.98
2005	4.07
2006	4.17
2007	4.26
2008	4.36
2009	4.46
2010	4.56
2011	4.66
2012	4.77
2013	4.87
2014	4.98
2015	5.08