# year    value 
 1960 10.05729 
 1961 10.25222 
 1962 10.26475 
 1963 10.70952 
 1964 9.785948 
 1965 9.894446 
 1966 10.07791 
 1967 10.26852 
 1968 9.910762 
 1969 10.04331 
 1970 9.986727 
 1971 9.832383 
 1972 9.855389 
 1973  10.1135 
 1974 10.37483 
 1975 9.533936 
 1976 10.16963 
 1977 10.68838 
 1978 9.808916 
 1979 9.689789 
 1980 10.62201 
 1981 11.21535 
 1982 9.555385 
 1983 10.19139 
 1984 10.05533 
 1985 9.555682 
 1986 10.92882 
 1987 10.92085 
 1988 10.71425 
 1989 10.18772 
 1990  10.7315 
 1991 10.55887 
 1992 10.75718 
 1993 9.659569 
 1994 10.94802 
 1995 10.79353 
 1996   10.364 
 1997  10.2441 
 1998 10.86348 
 1999 10.88502 
 2000 10.71172 
 2001 10.93129 
 2002 10.48467 
 2003 11.05212 
 2004 10.75209 
 2005 11.02122 
 2006  11.3957 
 2007    10.95 
 2008 10.34763 
 2009 10.35697 
 2010 10.64012 
 2011 10.52622 
 2012 11.84813 
 2013 10.47066 
 2014 11.00987 
 2015 11.74409 
 2016 11.81562 
 2017 11.39518 
 2018 11.05809