Year	Measure
1800	528.7
1820	528.7
1870	643.6
1913	896.3
1950	1491
1951	1520
1952	1547
1953	1574
1954	1602
1955	1457
1956	1918
1957	1886
1958	1990
1959	2050
1960	2088
1961	2407
1962	2348
1963	2375
1964	2672
1965	2853
1966	2812
1967	2742
1968	2396
1969	2485
1970	2147
1971	2120
1972	2111
1973	2141
1974	2246
1975	2315
1976	2775
1977	2852
1978	3333
1979	3513
1980	4015
1981	4035
1982	4161
1983	4084
1984	4272
1985	4261
1986	4483
1987	4449
1988	4257
1989	3677
1990	3399
1991	3124
1992	3432
1993	3524
1994	3611
1995	3732
1996	3669
1997	3645
1998	3625
1999	3626
2000	3665
2001	3743
2002	3845
2003	3894
2004	4116
2005	4294
2006	4536
2007	4802
2008	5037
2009	5198
2010	5202
2011	5217
2012	5243
2013	5291
2014	5354
2015	5443
2016	5560
2017	5680
2018	5802