Year Measure 1971 37113.33953 1972 36146.69961 1973 40710.11218 1974 37557.34036 1975 25763.47323 1976 28353.1282 1977 28090.6737 1978 25027.22106 1979 25303.04158 1980 26517.45125 1981 25001.64167 1982 27354.02163 1983 28902.85064 1984 19859.93813 1985 11685.01942 1986 11099.90043 1987 9544.03919 1988 8775.9926 1989 9465.43757 1990 10030.15131 1991 10062.53333 1992 10501.83445 1993 8854.51043 1994 8997.11678 1995 9055.71211 1996 9222.18501 1997 16175.1953 1998 18814.37234 1999 14680.92492 2000 15720.11056 2001 16994.13392 2002 16662.99292 2003 15566.69219 2004 16180.823 2005 15178.82724 2006 14581.1072 2007 16222.45516 2008 15326.48752 2009 15608.494 2010 13710.07982 2011 16064.05182 2012 13395.36979 2013 11727.50972 2014 12650.86044