Year	Measure
1800	775.1
1820	775.1
1913	1266
1950	2822
1951	2903
1952	3082
1953	3252
1954	3371
1955	3487
1956	3739
1957	3907
1958	3951
1959	4264
1960	4503
1961	4841
1962	5108
1963	5530
1964	5793
1965	6212
1966	6573
1967	6929
1968	7191
1969	7688
1970	8357
1971	8744
1972	9123
1973	9612
1974	9540
1975	9144
1976	9337
1977	9771
1978	10290
1979	10750
1980	10770
1981	10790
1982	10330
1983	10260
1984	10900
1985	11020
1986	11810
1987	12280
1988	12970
1989	13490
1990	13870
1991	14090
1992	14640
1993	15190
1994	15680
1995	16250
1996	16590
1997	17000
1998	17440
1999	18080
2000	18570
2001	18860
2002	18860
2003	19070
2004	19290
2005	19730
2006	19290
2007	18970
2008	18650
2009	18510
2010	18520
2011	18270