Year	Measure
1800	1391
1820	1420
1870	2080
1890	2806
1900	3206
1910	3812
1913	3998
1920	3257
1924	3644
1925	4343
1926	4120
1927	4264
1928	4602
1929	4718
1930	4581
1931	4323
1932	4178
1933	4524
1934	4516
1935	4710
1936	4990
1937	4846
1938	5061
1939	5408
1940	5005
1941	5005
1942	5227
1946	3279
1947	3380
1948	4193
1949	4487
1950	4726
1951	5136
1952	5264
1953	5308
1954	5432
1955	5851
1956	5538
1957	6040
1958	6417
1959	6640
1960	6954
1961	7273
1962	7550
1963	7943
1964	8362
1965	8403
1966	8854
1967	9327
1968	9403
1969	9647
1970	9582
1971	9983
1972	10170
1973	10660
1974	10890
1975	11060
1976	11040
1977	11670
1978	11920
1979	11910
1980	12020
1981	12100
1982	12550
1983	12440
1984	12790
1985	12500
1986	12770
1987	12990
1988	13400
1989	13160
1990	12310
1991	10850
1992	10540
1993	10490
1994	10820
1995	11000
1996	11170
1997	11710
1998	12320
1999	12870
2000	13590
2001	14190
2002	14840
2003	15510
2004	16290
2005	17010
2006	17710
2007	17750
2008	17920
2009	16750
2010	16980
2011	17310
2012	17070
2013	17100
2014	17340
2015	17630
2016	17960
2017	18290
2018	18620