Year	Measure
1800	619.2
1820	619.2
1913	415.1
1950	354.1
1951	358.1
1952	362.1
1953	376.6
1954	370.1
1955	383.2
1956	388.8
1957	378.9
1958	384.2
1959	387.3
1960	399.4
1961	410.9
1962	419.5
1963	465.6
1964	478.8
1965	496.7
1966	505.5
1967	516.1
1968	514
1969	521.8
1970	539.9
1971	550.8
1972	566.2
1973	571.9
1974	565.6
1975	553.4
1976	554.5
1977	556.8
1978	541.5
1979	569.3
1980	588.4
1981	584.6
1982	577.9
1983	590.6
1984	565.8
1985	520
1986	541.2
1987	573.7
1988	564.4
1989	552.6
1990	524.7
1991	489.8
1992	421.4
1993	462.4
1994	460.1
1995	471.4
1996	512.8
1997	515.9
1998	481.5
1999	496.9
2000	512.4
2001	537.4
2002	530.1
2003	498.4
2004	549.6
2005	591
2006	644.2
2007	704.2
2008	765.9
2009	824.8
2010	871.8
2011	917.5
2012	958.7
2013	997.1
2014	1037
2015	1081
2016	1126
2017	1173
2018	1225