Year	Years
1970	1.75
1971	1.81
1972	1.86
1973	1.92
1974	1.98
1975	2.04
1976	2.11
1977	2.17
1978	2.24
1979	2.31
1980	2.38
1981	2.45
1982	2.53
1983	2.61
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
1999	4.11
2000	4.23
2001	4.34
2002	4.46
2003	4.58
2004	4.7
2005	4.82
2006	4.95
2007	5.07
2008	5.2
2009	5.33
2010	5.47
2011	5.6
2012	5.74
2013	5.88
2014	6.02
2015	6.16