Year	Measure
1800	1031
1820	1066
1913	3155
1970	18030
1971	18200
1972	18790
1973	20070
1974	21090
1975	20480
1976	21660
1977	21860
1978	22160
1979	23060
1980	23470
1981	23330
1982	23110
1983	23100
1984	23570
1985	23950
1986	24350
1987	24850
1988	25600
1989	26160
1990	26390
1991	26450
1992	26310
1993	28240
1994	29840
1995	32270
1996	33560
1997	34140
1998	36450
1999	39350
2000	39600
2001	40970
2002	40070
2003	40560
2004	41430
2005	41590
2006	42600
2007	43680
2008	41960
2009	36420
2010	34340
2011	33230