Year	Measure
1971	539.42453
1972	527.04948
1973	513.38457
1974	495.38434
1975	480.04077
1976	469.78316
1977	455.45495
1978	446.50165
1979	436.90324
1980	429.00844
1981	421.70693
1982	414.7832
1983	410.27104
1984	405.48196
1985	401.50897
1986	398.9741
1987	394.24122
1988	389.42011
1989	385.8537
1990	382.29888
1991	377.45359
1992	369.62097
1993	367.10613
1994	361.86517
1995	367.88069
1996	362.14452
1997	356.11524
1998	369.67395
1999	383.0763
2000	393.87818
2001	404.83117
2002	413.72654
2003	417.98969
2004	430.49835
2005	437.52389
2006	439.61545
2007	441.1719
2008	441.87202
2009	440.1066
2010	448.22094
2011	459.15896
2012	472.28589
2013	474.35154
2014	475.42696