Year	Measure
1800	845.8
1820	849.8
1913	1458
1958	5100
1970	13680
1971	13240
1972	12700
1973	19450
1974	47590
1975	53500
1976	52630
1977	53340
1978	45590
1979	50730
1980	58180
1981	55160
1982	47210
1983	42150
1984	41480
1985	38210
1986	29230
1987	29330
1988	27050
1989	29060
1990	32430
1991	30830
1992	30080
1993	28310
1994	29010
1995	29340
1996	29290
1997	29990
1998	28680
1999	28250
2000	30010
2001	29450
2002	28730
2003	30650
2004	32180
2005	33490
2006	35390
2007	35530
2008	35250
2009	31560
2010	31040
2011	31700
2012	31980
2013	32020
2014	32210
2015	32390
2016	32660
2017	32920
2018	33200