Year	Years
1970	1.92
1971	1.97
1972	2.02
1973	2.07
1974	2.12
1975	2.18
1976	2.23
1977	2.29
1978	2.34
1979	2.4
1980	2.46
1981	2.52
1982	2.59
1983	2.65
1984	2.71
1985	2.78
1986	2.85
1987	2.92
1988	2.99
1989	3.06
1990	3.14
1991	3.21
1992	3.29
1993	3.37
1994	3.45
1995	3.54
1996	3.62
1997	3.71
1998	3.8
1999	3.89
2000	3.98
2001	4.08
2002	4.17
2003	4.27
2004	4.37
2005	4.47
2006	4.57
2007	4.67
2008	4.78
2009	4.89
2010	4.99
2011	5.1
2012	5.21
2013	5.33
2014	5.44
2015	5.56