# year    value 
 1980 11.35856 
 1981 11.58113 
 1982 10.18552 
 1983 11.58367 
 1984 10.09911 
 1985   9.0072 
 1986 10.17572 
 1987 11.58167 
 1988 11.50565 
 1989 11.18808 
 1990 11.97028 
 1991 10.69144 
 1992 10.86072 
 1993 9.885124 
 1994 11.16421 
 1995 11.69265 
 1996 10.39548 
 1997 11.25941 
 1998 12.08078 
 1999 11.87107 
 2000 9.981431 
 2001 12.20498 
 2002 10.50561 
 2003  11.2893 
 2004 11.29421 
 2005 11.98811 
 2006 10.76773 
 2007 11.81298 
 2008 11.64499 
 2009 11.30032 
 2010 11.64322 
 2011 11.73971 
 2012 12.03433 
 2013 11.28311 
 2014  11.7989 
 2015 12.65202 
 2016 13.05122 
 2017 12.11276 
 2018 10.87987