Year	Years
1970	1.7
1971	1.75
1972	1.79
1973	1.84
1974	1.89
1975	1.94
1976	1.99
1977	2.04
1978	2.1
1979	2.15
1980	2.21
1981	2.26
1982	2.32
1983	2.38
1984	2.44
1985	2.51
1986	2.57
1987	2.64
1988	2.7
1989	2.77
1990	2.84
1991	2.91
1992	2.98
1993	3.06
1994	3.13
1995	3.21
1996	3.29
1997	3.37
1998	3.45
1999	3.53
2000	3.61
2001	3.69
2002	3.78
2003	3.87
2004	3.95
2005	4.04
2006	4.13
2007	4.23
2008	4.32
2009	4.41
2010	4.51
2011	4.6
2012	4.7
2013	4.8
2014	4.9
2015	5.01