Year	Measure
1800	853.2
1820	853.2
1913	1574
1970	4842
1971	5248
1972	5636
1973	6026
1974	6443
1975	6912
1976	7448
1977	8047
1978	8689
1979	9343
1980	9979
1981	10580
1982	11150
1983	11730
1984	12380
1985	13110
1986	13960
1987	14890
1988	15920
1989	17000
1990	17910
1991	18700
1992	19340
1993	20370
1994	21750
1995	22180
1996	23260
1997	24060
1998	25700
1999	26820
2000	26820
2001	27160
2002	25900
2003	26730
2004	28340
2005	31210
2006	34470
2007	35750
2008	37370
2009	32050
2010	33480
2011	34780