Year Measure 1971 327.56697 1972 308.40764 1973 399.84162 1974 364.38088 1975 402.33518 1976 381.1978 1977 421.29654 1978 409.30694 1979 471.28832 1980 440.8472 1981 442.49344 1982 327.53067 1983 365.25378 1984 443.19737 1985 474.96816 1986 482.75556 1987 476.30142 1988 379.09318 1989 333.38364 1990 388.52132 1991 398.32795 1992 540.26544 1993 508.44351 1994 526.37336 1995 497.05901 1996 633.44482 1997 636.98387 1998 1090.35573 1999 1267.7492 2000 1313.61632 2001 1273.63913 2002 1373.48376 2003 1347.38218 2004 1112.60049 2005 1215.90471 2006 1308.56448 2007 1335.38811 2008 1352.35541 2009 1299.7865 2010 1366.23767 2011 1397.61317 2012 1466.27999 2013 1516.54033 2014 1578.15166