1979      2.32
1980     11.56
1981      3.03
1982      5.87
1983      6.87
1984      1.89
1985     -1.52
1986      7.15
1987      6.30
1988      6.44
1989      0.05
1990    -11.32
1991     -6.92
1992      7.29
1993     -7.63
1994      2.03
1995    -12.89
1996     11.98
1997     -4.22
1998     -6.78
1999    -11.32
2000    -10.19
2001     -4.08
2002    -15.30
2003    -12.60
2004    -14.02
2005    -20.84
2006    -15.87
2007    -38.89
2008    -32.78
2009    -23.40
2010    -29.94
2011    -34.49
2012    -48.70