Year	Years
1970	1.62
1971	1.67
1972	1.72
1973	1.78
1974	1.83
1975	1.89
1976	1.95
1977	2.01
1978	2.08
1979	2.14
1980	2.21
1981	2.28
1982	2.35
1983	2.43
1984	2.5
1985	2.58
1986	2.66
1987	2.75
1988	2.83
1989	2.92
1990	3.01
1991	3.11
1992	3.2
1993	3.3
1994	3.41
1995	3.51
1996	3.63
1997	3.74
1998	3.86
1999	3.98
2000	4.1
2001	4.23
2002	4.35
2003	4.48
2004	4.61
2005	4.74
2006	4.88
2007	5.01
2008	5.15
2009	5.29
2010	5.44
2011	5.58
2012	5.73
2013	5.87
2014	6.02
2015	6.17