Year	Years
1970	1
1971	1.03
1972	1.06
1973	1.1
1974	1.14
1975	1.17
1976	1.21
1977	1.26
1978	1.3
1979	1.34
1980	1.39
1981	1.44
1982	1.49
1983	1.55
1984	1.6
1985	1.66
1986	1.72
1987	1.78
1988	1.85
1989	1.92
1990	1.99
1991	2.06
1992	2.14
1993	2.21
1994	2.29
1995	2.38
1996	2.44
1997	2.51
1998	2.58
1999	2.65
2000	2.72
2001	2.8
2002	2.87
2003	2.94
2004	3.02
2005	3.1
2006	3.18
2007	3.25
2008	3.34
2009	3.42
2010	3.5
2011	3.59
2012	3.67
2013	3.76
2014	3.85
2015	3.94