Year	Years
1970	1.92
1971	1.97
1972	2.03
1973	2.08
1974	2.13
1975	2.19
1976	2.24
1977	2.3
1978	2.36
1979	2.42
1980	2.48
1981	2.54
1982	2.61
1983	2.67
1984	2.74
1985	2.81
1986	2.88
1987	2.95
1988	3.02
1989	3.09
1990	3.16
1991	3.24
1992	3.31
1993	3.39
1994	3.47
1995	3.55
1996	3.62
1997	3.7
1998	3.78
1999	3.86
2000	3.94
2001	4.02
2002	4.11
2003	4.19
2004	4.28
2005	4.37
2006	4.45
2007	4.54
2008	4.64
2009	4.73
2010	4.83
2011	4.92
2012	5.02
2013	5.12
2014	5.22
2015	5.33