Year Measure 1971 339.45104 1972 348.93197 1973 359.86696 1974 367.87791 1975 372.24174 1976 365.39594 1977 381.51511 1978 374.54994 1979 370.53517 1980 372.47413 1981 378.63362 1982 376.70909 1983 308.65914 1984 318.74313 1985 342.25566 1986 345.3601 1987 363.82444 1988 346.4338 1989 363.56877 1990 361.69941 1991 364.0474 1992 366.70451 1993 373.77872 1994 378.60399 1995 386.10404 1996 389.55904 1997 397.3222 1998 409.9972 1999 415.65019 2000 331.40318 2001 325.2379 2002 315.11321 2003 290.54274 2004 282.90419 2005 273.19648 2006 283.53365 2007 276.22694 2008 269.14876 2009 284.11613 2010 302.17455 2011 314.72682 2012 332.52764 2013 339.80615 2014 335.05053