Year	Measure
1800	359.9
1820	359.9
1913	556.1
1950	3363
1951	3441
1952	3521
1953	3599
1954	3451
1955	3672
1956	3549
1957	3828
1958	3966
1959	3918
1960	4006
1961	4464
1962	4269
1963	4414
1964	4826
1965	5102
1966	5308
1967	5523
1968	5347
1969	5408
1970	5652
1971	5526
1972	5473
1973	5722
1974	5470
1975	3431
1976	3050
1977	3009
1978	3071
1979	3065
1980	3075
1981	2953
1982	2757
1983	2585
1984	2527
1985	2493
1986	2221
1987	2430
1988	2729
1989	2731
1990	2777
1991	2731
1992	2628
1993	1870
1994	1851
1995	1989
1996	2157
1997	2277
1998	2384
1999	2417
2000	2447
2001	2480
2002	2773
2003	2785
2004	3007
2005	3533
2006	4148
2007	4950
2008	5488
2009	5476
2010	5498
2011	5547
2012	5838
2013	6018
2014	6268
2015	6512
2016	6744
2017	6729
2018	6928