Year	Years
1970	1.78
1971	1.83
1972	1.87
1973	1.92
1974	1.97
1975	2.02
1976	2.07
1977	2.13
1978	2.18
1979	2.24
1980	2.3
1981	2.35
1982	2.41
1983	2.47
1984	2.54
1985	2.6
1986	2.67
1987	2.73
1988	2.8
1989	2.87
1990	2.94
1991	3.02
1992	3.09
1993	3.17
1994	3.24
1995	3.32
1996	3.41
1997	3.49
1998	3.58
1999	3.66
2000	3.75
2001	3.84
2002	3.93
2003	4.03
2004	4.12
2005	4.22
2006	4.32
2007	4.42
2008	4.52
2009	4.62
2010	4.72
2011	4.83
2012	4.93
2013	5.04
2014	5.15
2015	5.26