Year	Measure
1800	809.3
1820	809.3
1913	1094
1938	3809
1950	6932
1965	14650
1966	15500
1967	14240
1968	15790
1969	14830
1970	14560
1971	15780
1972	14570
1973	15220
1974	17410
1975	16060
1976	16850
1977	16680
1978	17780
1979	17930
1980	17490
1981	18420
1982	19670
1983	20150
1984	20670
1985	21220
1986	22430
1987	23450
1988	23470
1989	23640
1990	23650
1991	24290
1992	24020
1993	23570
1994	23310
1995	22980
1996	22620
1997	22630
1998	23610
1999	24120
2000	24660
2001	24580
2002	25220
2003	25630
2004	25650
2005	26020
2006	25980
2007	26210
2008	26350
2009	26450
2010	26560
2011	26700