1979      1.13
1980      1.88
1981     -1.03
1982      7.48
1983      3.82
1984     -4.80
1985     -4.37
1986      6.51
1987      0.05
1988      1.99
1989      2.53
1990      0.70
1991     -1.35
1992      3.39
1993     -1.14
1994      2.10
1995     -3.72
1996      1.13
1997     -5.66
1998     -4.69
1999     -2.00
2000     -3.94
2001     -7.49
2002     -5.12
2003     -6.84
2004     -8.67
2005     -9.00
2006    -10.29
2007    -27.09
2008     -9.32
2009    -19.01
2010    -16.97
2011    -23.54