Year	Measure
1800	539.6
1820	539.6
1950	683.5
1970	835.9
1971	828.3
1972	807.6
1973	789.3
1974	799.5
1975	745.3
1976	783.5
1977	816.3
1978	845.5
1979	858.1
1980	874.6
1981	948.7
1982	946.8
1983	999.7
1984	1036
1985	1065
1986	1178
1987	1494
1988	1535
1989	1615
1990	1782
1991	1805
1992	1904
1993	1989
1994	2149
1995	2317
1996	2456
1997	2562
1998	2656
1999	2790
2000	2922
2001	3046
2002	3256
2003	3406
2004	3546
2005	3694
2006	3857
2007	4457
2008	4580
2009	4804
2010	5274
2011	5627
2012	6131
2013	6505
2014	7053
2015	7664
2016	8755
2017	9670
2018	10620