Year	Measure
1800	661.9
1820	665
1913	1141
1938	1319
1950	104200
1951	107500
1952	108400
1953	113200
1954	119800
1955	116400
1956	118700
1957	113500
1958	108000
1959	106700
1960	104000
1961	94260
1962	95460
1963	91440
1964	91340
1965	84950
1966	86820
1967	80890
1968	80500
1969	75680
1970	110800
1971	111700
1972	109300
1973	96340
1974	79180
1975	65560
1976	65580
1977	59270
1978	59710
1979	63800
1980	47910
1981	37150
1982	31350
1983	32370
1984	32580
1985	29470
1986	30590
1987	28120
1988	27900
1989	28760
1990	22100
1991	29270
1992	34930
1993	44800
1994	46470
1995	44960
1996	41620
1997	40300
1998	38060
1999	36010
2000	36400
2001	35250
2002	35110
2003	39560
2004	42280
2005	44950
2006	45420
2007	45070
2008	45620
2009	41870
2010	39770
2011	41130
2012	42050
2013	41340
2014	41480
2015	41900
2016	42330
2017	42780
2018	43250