Year	Measure
1800	490.8
1820	501.1
1870	402.6
1890	566.6
1900	606.3
1910	710.4
1913	710.4
1920	693.1
1921	700
1922	710.3
1923	736.7
1924	778.4
1925	805.1
1926	849.2
1927	823.6
1928	883.4
1929	916.9
1930	886.2
1931	847.4
1932	758
1933	770.9
1934	788.6
1935	766.1
1936	853.7
1937	856
1938	911.7
1939	948.9
1947	884.2
1948	1041
1949	1128
1950	1042
1951	1069
1952	973.5
1953	1104
1954	1151
1955	1208
1956	1171
1957	1354
1958	1398
1959	1555
1960	1638
1961	1695
1962	1710
1963	1869
1964	2029
1965	2064
1966	2154
1967	2172
1968	2200
1969	2426
1970	2524
1971	2790
1972	2860
1973	2931
1974	3280
1975	3251
1976	3320
1977	3528
1978	3691
1979	3911
1980	4075
1981	4123
1982	4127
1983	4139
1984	4220
1985	4232
1986	4384
1987	4314
1988	4235
1989	4163
1990	3845
1991	3378
1992	2547
1993	1896
1994	2034
1995	2201
1996	3488
1997	4766
1998	5251
1999	5545
2000	5733
2001	5881
2002	6019
2003	6098
2004	6317
2005	6506
2006	6893
2007	7320
2008	7740
2009	7528
2010	7596
2011	7706
2012	7664
2013	7715
2014	7883
2015	8175
2016	8521
2017	8884
2018	9257