Year	Measure
1820	1503
1821	1499
1822	1496
1823	1492
1824	1488
1825	1485
1826	1481
1827	1478
1828	1474
1829	1471
1830	1467
1831	1464
1832	1460
1833	1457
1834	1453
1835	1450
1836	1447
1837	1443
1838	1440
1839	1436
1840	1433
1841	1429
1842	1426
1843	1423
1844	1419
1845	1416
1846	1413
1847	1409
1848	1406
1849	1403
1850	1399
1851	1396
1852	1393
1853	1389
1854	1386
1855	1383
1856	1379
1857	1376
1858	1373
1859	1370
1860	1366
1861	1363
1862	1360
1863	1357
1864	1353
1865	1350
1866	1347
1867	1344
1868	1341
1869	1337
1870	1334
1871	1362
1872	1390
1873	1418
1874	1447
1875	1477
1876	1507
1877	1538
1878	1569
1879	1601
1880	1634
1881	1668
1882	1702
1883	1737
1884	1772
1885	1809
1886	1846
1887	1884
1888	1922
1889	1962
1890	2002
1891	2047
1892	2094
1893	2142
1894	2191
1895	2241
1896	2277
1897	2396
1898	2498
1899	2340
1900	2323
1901	2497
1902	2292
1903	2524
1904	2541
1905	2777
1906	2716
1907	2846
1908	2810
1909	2862
1910	2857
1911	2742
1912	2719
1913	2555
1914	2560
1915	2523
1916	2717
1917	2833
1918	2944
1919	3061
1920	3256
1921	3244
1922	3267
1923	3327
1924	3220
1925	3367
1926	3515
1927	3304
1928	3271
1929	3092
1930	2848
1931	2893
1932	2411
1933	2642
1934	2775
1935	2933
1936	3116
1937	3165
1938	3162
1939	3277
1940	3266
1941	3494
1942	3594
1943	3628
1944	3824
1945	3839
1946	3985
1947	4013
1948	4067
1949	4178
1950	4477
1951	4685
1952	4727
1953	4595
1954	4913
1955	5179
1956	5373
1957	5615
1958	5741
1959	5736
1960	6025
1961	6132
1962	6227
1963	6529
1964	7086
1965	7319
1966	7590
1967	7821
1968	8204
1969	8457
1970	8767
1971	8816
1972	9255
1973	9691
1974	9951
1975	10220
1976	10370
1977	10430
1978	11090
1979	11870
1980	12670
1981	13440
1982	13060
1983	12320
1984	12470
1985	12480
1986	11840
1987	11810
1988	11730
1989	11980
1990	12370
1991	12660
1992	12870
1993	12890
1994	13230
1995	12170
1996	12610
1997	13270
1998	13740
1999	14080
2000	14810
2001	14630
2002	14600
2003	14650
2004	15110
2005	15380
2006	15960
2007	16210
2008	16130
2009	14920
2010	15480
2011	15890
2012	16310
2013	16300
2014	16620
2015	17030
2016	17500
2017	17970
2018	18460
2019	18970