Year	Years
1970	1
1971	1.04
1972	1.07
1973	1.1
1974	1.14
1975	1.18
1976	1.22
1977	1.26
1978	1.3
1979	1.35
1980	1.4
1981	1.45
1982	1.5
1983	1.55
1984	1.61
1985	1.67
1986	1.74
1987	1.81
1988	1.88
1989	1.96
1990	2.05
1991	2.14
1992	2.24
1993	2.35
1994	2.47
1995	2.59
1996	2.71
1997	2.82
1998	2.93
1999	3.04
2000	3.15
2001	3.26
2002	3.37
2003	3.48
2004	3.59
2005	3.7
2006	3.81
2007	3.92
2008	4.03
2009	4.14
2010	4.26
2011	4.37
2012	4.49
2013	4.6
2014	4.72
2015	4.84