Year	Measure
1800	572.8
1820	592.1
1913	1753
1950	2921
1970	6324
1971	7126
1972	7625
1973	7846
1974	7689
1975	6454
1976	7681
1977	8898
1978	9539
1979	10410
1980	10900
1981	11100
1982	11660
1983	12130
1984	13020
1985	13470
1986	13820
1987	14630
1988	15680
1989	16700
1990	17570
1991	17240
1992	18360
1993	18040
1994	18700
1995	20180
1996	20230
1997	20410
1998	21170
1999	21950
2000	22820
2001	23470
2002	23680
2003	23770
2004	24210
2005	24470
2006	25020
2007	25660
2008	25900
2009	24730
2010	24440
2011	23930
2012	23090