| Year | Anomaly | Trend |
|---|---|---|
| 1980 | 18.91 | 16.76 |
| 1981 | 35.83 | 15.8 |
| 1982 | 18.3 | 14.85 |
| 1983 | -11.39 | 13.89 |
| 1984 | 27.03 | 12.93 |
| 1985 | 23.01 | 11.97 |
| 1986 | 14.93 | 11.01 |
| 1987 | 28.34 | 10.06 |
| 1988 | 41.85 | 9.1 |
| 1989 | -8.06 | 8.14 |
| 1990 | -34.89 | 7.18 |
| 1991 | -19.88 | 6.23 |
| 1992 | -32.4 | 5.27 |
| 1993 | -9.46 | 4.31 |
| 1994 | 20.41 | 3.35 |
| 1995 | 2.62 | 2.39 |
| 1996 | 17.37 | 1.44 |
| 1997 | -13.27 | 0.48 |
| 1998 | 2.26 | -0.48 |
| 1999 | 10.55 | -1.44 |
| 2000 | 19.21 | -2.39 |
| 2001 | -15.41 | -3.35 |
| 2002 | -7.57 | -4.31 |
| 2003 | -12.84 | -5.27 |
| 2004 | -14.73 | -6.23 |
| 2005 | -10.54 | -7.18 |
| 2006 | 24.26 | -8.14 |
| 2007 | -27.19 | -9.1 |
| 2008 | -17.87 | -10.06 |
| 2009 | -10.88 | -11.02 |
| 2010 | 18.83 | -11.97 |
| 2011 | 17.47 | -12.93 |
| 2012 | -12.41 | -13.89 |
| 2013 | 3.64 | -14.85 |
| 2014 | -47.9 | -15.8 |
| 2015 | -38.15 | -16.76 |