Year	Years
1970	1.54
1971	1.59
1972	1.65
1973	1.7
1974	1.76
1975	1.82
1976	1.88
1977	1.94
1978	2
1979	2.07
1980	2.14
1981	2.21
1982	2.28
1983	2.36
1984	2.43
1985	2.51
1986	2.59
1987	2.68
1988	2.77
1989	2.85
1990	2.95
1991	3.04
1992	3.14
1993	3.24
1994	3.34
1995	3.45
1996	3.56
1997	3.68
1998	3.79
1999	3.91
2000	4.03
2001	4.16
2002	4.28
2003	4.41
2004	4.53
2005	4.66
2006	4.79
2007	4.93
2008	5.06
2009	5.2
2010	5.33
2011	5.47
2012	5.61
2013	5.75
2014	5.89
2015	6.03