Year	Years
1970	1.74
1971	1.8
1972	1.86
1973	1.92
1974	1.98
1975	2.04
1976	2.1
1977	2.17
1978	2.24
1979	2.31
1980	2.38
1981	2.45
1982	2.53
1983	2.6
1984	2.68
1985	2.76
1986	2.85
1987	2.93
1988	3.02
1989	3.11
1990	3.2
1991	3.29
1992	3.39
1993	3.49
1994	3.59
1995	3.69
1996	3.79
1997	3.9
1998	4.01
1999	4.12
2000	4.23
2001	4.34
2002	4.46
2003	4.57
2004	4.69
2005	4.82
2006	4.94
2007	5.06
2008	5.19
2009	5.32
2010	5.45
2011	5.59
2012	5.72
2013	5.86
2014	6
2015	6.14