Year	Measure
1800	549.2
1820	549.2
1913	848.5
1950	1344
1951	1367
1952	1389
1953	1410
1954	1433
1955	1456
1956	1478
1957	1501
1958	1523
1959	1538
1960	1623
1961	1715
1962	1729
1963	1936
1964	2192
1965	2056
1966	2120
1967	2052
1968	2258
1969	2245
1970	2367
1971	2365
1972	2378
1973	2453
1974	2421
1975	2325
1976	2501
1977	2518
1978	2661
1979	2609
1980	2705
1981	2696
1982	2603
1983	2412
1984	2250
1985	2279
1986	2267
1987	2157
1988	2049
1989	1973
1990	1760
1991	1693
1992	1648
1993	1599
1994	1578
1995	1641
1996	1724
1997	1786
1998	1840
1999	1830
2000	1746
2001	1710
2002	1649
2003	1587
2004	1579
2005	1575
2006	1540
2007	1519
2008	1509
2009	1520
2010	1512
2011	1399
2012	1492
2013	1563
2014	1639
2015	1719
2016	1800
2017	1877
2018	1949