Year	Measure
1800	377.5
1820	377.5
1913	583.3
1950	4041
1951	4166
1952	4293
1953	4422
1954	4556
1955	4695
1956	4834
1957	4976
1958	5122
1959	5269
1960	5440
1961	6209
1962	6631
1963	6989
1964	7256
1965	7803
1966	8094
1967	8359
1968	8487
1969	9060
1970	9692
1971	10480
1972	11400
1973	12250
1974	16650
1975	19330
1976	25540
1977	21750
1978	16080
1979	15730
1980	15700
1981	16040
1982	15110
1983	15510
1984	16190
1985	15350
1986	14770
1987	11860
1988	12980
1989	13660
1990	13940
1991	14360
1992	13520
1993	13660
1994	13790
1995	14110
1996	14260
1997	14720
1998	14890
1999	13280
2000	12760
2001	12790
2002	12520
2003	12610
2004	12570
2005	12740
2006	12190
2007	12510
2008	12450
2009	11920
2010	12540
2011	13230
2012	13850
2013	14480
2014	15250
2015	16070
2016	16980
2017	18000
2018	18150