Year	Measure
1800	400.9
1820	414.5
1913	1227
1970	16160
1971	17880
1972	18680
1973	19700
1974	20640
1975	20630
1976	21780
1977	23670
1978	25080
1979	26240
1980	28390
1981	28340
1982	26790
1983	27360
1984	25610
1985	26220
1986	27770
1987	28990
1988	30330
1989	32120
1990	28200
1991	28100
1992	26650
1993	25330
1994	26860
1995	27860
1996	28270
1997	28630
1998	30770
1999	31100
2000	33200
2001	33510
2002	33050
2003	32790
2004	33510
2005	33990
2006	36170
2007	37010
2008	37870
2009	38410
2010	38870
2011	39870