Year	Measure
1800	497.2
1820	497.2
1870	651.1
1913	821.4
1950	1683
1951	1686
1952	1688
1953	1698
1954	1707
1955	1715
1956	1678
1957	1642
1958	1606
1959	1571
1960	1537
1961	1551
1962	1566
1963	1581
1964	1597
1965	1612
1966	1661
1967	1711
1968	1763
1969	1815
1970	1869
1971	1925
1972	1930
1973	1959
1974	2025
1975	2117
1976	2304
1977	2371
1978	2393
1979	2454
1980	2628
1981	2509
1982	2703
1983	2617
1984	2655
1985	2749
1986	2890
1987	2755
1988	2964
1989	2960
1990	3002
1991	3138
1992	2948
1993	2857
1994	3090
1995	2829
1996	3112
1997	2982
1998	3157
1999	3097
2000	3073
2001	3211
2002	3258
2003	3400
2004	3519
2005	3547
2006	3780
2007	3841
2008	4011
2009	4157
2010	4263
2011	4429
2012	4515
2013	4671
2014	4846
2015	5041
2016	5261
2017	5509
2018	5773