Year	Measure
1800	498.8
1820	498.8
1913	770.7
1950	1079
1951	1121
1952	1136
1953	1157
1954	1201
1955	1216
1956	1237
1957	1258
1958	1267
1959	1314
1960	1304
1961	1339
1962	1369
1963	1393
1964	1216
1965	1111
1966	1242
1967	1285
1968	1278
1969	1094
1970	1163
1971	1166
1972	1255
1973	1201
1974	933.8
1975	1227
1976	1192
1977	1451
1978	1419
1979	1206
1980	1059
1981	1137
1982	1177
1983	1038
1984	1038
1985	1080
1986	1076
1987	1093
1988	1089
1989	1112
1990	1106
1991	1030
1992	927
1993	933.1
1994	942.5
1995	952.5
1996	956.1
1997	930.6
1998	902.1
1999	891.9
2000	881.5
2001	868.9
2002	882.1
2003	895.7
2004	914
2005	933
2006	934.4
2007	938.3
2008	942.3
2009	945.8
2010	948.5
2011	949.8
2012	953.3