Year Measure 1971 50.77255 1972 49.91787 1973 56.88074 1974 67.28746 1975 55.10178 1976 60.84869 1977 56.41434 1978 59.74371 1979 36.34797 1980 36.46083 1981 36.01725 1982 47.62579 1983 37.21053 1984 29.0187 1985 30.96022 1986 36.44207 1987 41.54871 1988 33.91642 1989 38.89855 1990 41.36583 1991 54.66463 1992 53.08704 1993 49.73698 1994 43.50385 1995 45.37052 1996 45.05106 1997 53.46873 1998 48.14207 1999 67.89928 2000 123.14803 2001 271.88476 2002 260.55847 2003 367.15259 2004 440.02017 2005 441.76118 2006 449.05519 2007 449.15387 2008 432.35894 2009 431.89818 2010 440.39559 2011 440.67516 2012 445.38597 2013 436.13671 2014 462.62029