Year	Measure
1800	1054
1820	1106
1870	981.8
1890	1473
1895	1649
1896	1675
1897	1763
1898	1838
1899	1722
1900	1709
1901	1838
1902	1687
1903	1857
1904	1870
1905	2044
1906	1998
1907	2094
1908	2068
1909	2106
1910	2102
1911	2018
1912	2001
1913	1880
1914	1884
1915	1856
1916	1999
1917	2085
1918	2166
1919	2252
1920	2395
1921	2387
1922	2404
1923	2448
1924	2369
1925	2478
1926	2586
1927	2431
1928	2407
1929	2275
1930	2096
1931	2129
1932	1774
1933	1944
1934	2042
1935	2158
1936	2293
1937	2329
1938	2326
1939	2411
1940	2403
1941	2571
1942	2644
1943	2669
1944	2814
1945	2824
1946	2932
1947	2952
1948	2993
1949	3074
1950	3294
1951	3447
1952	3478
1953	3381
1954	3615
1955	3811
1956	3954
1957	4132
1958	4224
1959	4220
1960	4433
1961	4512
1962	4582
1963	4804
1964	5214
1965	5385
1966	5585
1967	5755
1968	6037
1969	6222
1970	6451
1971	6487
1972	6809
1973	7130
1974	7322
1975	7519
1976	7631
1977	7675
1978	8157
1979	8735
1980	9320
1981	9890
1982	9611
1983	9063
1984	9177
1985	9185
1986	8713
1987	8688
1988	8628
1989	8815
1990	9103
1991	9316
1992	9472
1993	9482
1994	9734
1995	8955
1996	9275
1997	9767
1998	10110
1999	10360
2000	10890
2001	10760
2002	10740
2003	10780
2004	11120
2005	11320
2006	11740
2007	11920
2008	11870
2009	10980
2010	11390
2011	11690
2012	12030
2013	12310
2014	12610
2015	12900
2016	13190
2017	13500
2018	13800