Year	Measure
1800	748.5
1820	748.5
1950	773.4
1951	783
1952	792.3
1953	801.2
1954	809.7
1955	818.3
1956	825.9
1957	833.6
1958	841.6
1959	848.9
1960	856.7
1961	865
1962	873.1
1963	881.1
1964	890
1965	898.1
1966	907.1
1967	915.9
1968	924.9
1969	934.1
1970	943.4
1971	952.9
1972	962.4
1973	971.7
1974	980.5
1975	988.7
1976	1015
1977	1036
1978	1054
1979	1080
1980	1105
1981	1125
1982	1134
1983	1141
1984	1149
1985	1159
1986	1162
1987	1164
1988	1167
1989	1170
1990	1172
1991	1175
1992	1203
1993	1287
1994	1329
1995	1362
1996	1359
1997	1395
1998	1401
1999	1472
2000	1518
2001	1565
2002	1616
2003	1668
2004	1732
2005	1811
2006	1938
2007	2058
2008	2185
2009	2314
2010	2467
2011	2628
2012	2807
2013	2990
2014	3177
2015	3377
2016	3593
2017	3819
2018	4053