Year	Measure
1800	527.4
1820	527.4
1913	973.1
1970	3300
1971	2922
1972	2879
1973	2997
1974	3253
1975	3368
1976	3335
1977	3379
1978	3615
1979	3988
1980	4460
1981	4364
1982	4311
1983	4385
1984	4433
1985	4298
1986	4262
1987	4664
1988	4961
1989	5175
1990	6846
1991	9053
1992	12080
1993	16380
1994	21430
1995	28300
1996	30790
1997	33270
1998	35910
1999	38530
2000	42980
2001	43880
2002	41720
2003	38210
2004	41710
2005	44960
2006	45040
2007	44840
2008	45010
2009	46470
2010	48040
2011	48740