Year Measure 1800 472.1 1820 472.1 1913 638.4 1950 757.3 1951 766.8 1952 779.4 1953 812.9 1954 815.4 1955 816.4 1956 837.1 1957 820.9 1958 849.7 1959 856.2 1960 868.5 1961 857.4 1962 853.1 1963 849.4 1964 846.3 1965 845.2 1966 833.6 1967 836.2 1968 845.1 1969 837.6 1970 833.3 1971 773.7 1972 740 1973 803.5 1974 825.6 1975 846.4 1976 866.2 1977 786.1 1978 827.1 1979 809.1 1980 810.4 1981 896.9 1982 978 1983 1013 1984 994.6 1985 961.9 1986 1031 1987 852.4 1988 770 1989 751.4 1990 709.5 1991 705.4 1992 649.3 1993 558.9 1994 500.4 1995 601.9 1996 617.9 1997 635.3 1998 653.3 1999 671 2000 663.9 2001 595 2002 726.7 2003 785.1 2004 804.7 2005 874 2006 887.9 2007 983.7 2008 984.8 2009 1155 2010 1215 2011 1261 2012 1350 2013 1351 2014 1374 2015 1418 2016 1462 2017 1501 2018 1527