Year Measure 1971 10.68879 1972 10.50335 1973 15.16934 1974 16.8564 1975 16.98316 1976 17.27418 1977 18.24469 1978 21.43214 1979 20.96249 1980 18.68153 1981 22.30019 1982 25.20715 1983 28.71916 1984 31.59843 1985 32.6288 1986 36.92198 1987 38.32473 1988 41.33683 1989 49.17025 1990 48.36675 1991 48.96648 1992 58.6485 1993 65.20947 1994 68.96922 1995 75.90125 1996 79.49228 1997 81.24847 1998 86.16983 1999 94.27288 2000 101.48863 2001 111.69426 2002 119.27467 2003 125.45767 2004 160.25336 2005 170.68125 2006 190.91546 2007 199.83119 2008 201.24886 2009 219.24206 2010 239.83053 2011 257.63437 2012 274.87196 2013 292.75003 2014 310.39123