Year	Years
1970	1.98
1971	2.03
1972	2.08
1973	2.13
1974	2.19
1975	2.24
1976	2.3
1977	2.36
1978	2.41
1979	2.47
1980	2.54
1981	2.6
1982	2.66
1983	2.73
1984	2.79
1985	2.86
1986	2.93
1987	3
1988	3.07
1989	3.15
1990	3.22
1991	3.3
1992	3.37
1993	3.45
1994	3.54
1995	3.62
1996	3.71
1997	3.8
1998	3.89
1999	3.99
2000	4.08
2001	4.18
2002	4.28
2003	4.38
2004	4.48
2005	4.59
2006	4.69
2007	4.8
2008	4.91
2009	5.02
2010	5.13
2011	5.24
2012	5.36
2013	5.47
2014	5.59
2015	5.7