| Year | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2022 | 5.40 | 6.10 | 7 | 9 | 9 | 9.40 | 10.10 | |||||
| 2021 | 0.70 | 0.50 | 0.70 | 1.50 | 2.10 | 2.50 | 2 | 3.20 | 3 | 4.10 | 5.10 | 5.40 |
| 2020 | 1.80 | 1.70 | 1.50 | 0.80 | 0.60 | 0.60 | 1.10 | 0.20 | 0.60 | 0.70 | 0.40 | 0.60 |
| 2019 | 1.80 | 1.80 | 1.90 | 2.10 | 2 | 2 | 2 | 1.80 | 1.80 | 1.50 | 1.40 | 1.30 |
| 2018 | 3 | 2.70 | 2.40 | 2.40 | 2.40 | 2.40 | 2.50 | 2.60 | 2.40 | 2.40 | 2.30 | 2.10 |
| 2017 | 1.90 | 2.30 | 2.30 | 2.70 | 2.90 | 2.70 | 2.60 | 2.90 | 3 | 3 | 3.20 | 2.90 |
| 2016 | 0.20 | 0.30 | 0.50 | 0.30 | 0.30 | 0.40 | 0.60 | 0.60 | 0.90 | 0.90 | 1.10 | 1.60 |
| 2015 | 0.30 | 0 | 0 | -0.20 | 0.10 | 0 | 0.10 | 0.10 | -0.10 | -0.10 | 0.20 | 0.20 |
| 2014 | 2 | 1.70 | 1.60 | 1.80 | 1.50 | 1.90 | 1.60 | 1.50 | 1.20 | 1.30 | 0.90 | 0.50 |
| 2013 | 2.60 | 2.80 | 2.80 | 2.40 | 2.70 | 2.90 | 2.80 | 2.70 | 2.70 | 2.20 | 2.10 | 2 |
| 2012 | 3.60 | 3.40 | 3.50 | 3 | 2.70 | 2.40 | 2.50 | 2.50 | 2.20 | 2.60 | 2.70 | 2.60 |
| 2011 | 4 | 4.30 | 3.90 | 4.50 | 4.50 | 4.20 | 4.50 | 4.50 | 5.10 | 5 | 4.80 | 4.30 |
| 2010 | 3.40 | 3 | 3.40 | 3.70 | 3.50 | 3.20 | 3 | 3.20 | 3.10 | 3.20 | 3.20 | 3.60 |
| 2009 | 3 | 3.10 | 2.90 | 2.40 | 2.10 | 1.80 | 1.90 | 1.50 | 1.20 | 1.50 | 2 | 2.90 |
| 2008 | 2.20 | 2.50 | 2.50 | 2.90 | 3.40 | 3.90 | 4.40 | 4.80 | 5.10 | 4.40 | 4 | 3 |
| 2007 | 2.70 | 2.80 | 3.20 | 2.80 | 2.40 | 2.40 | 1.90 | 1.70 | 1.70 | 2.10 | 2.10 | 2.10 |
| 2006 | 1.90 | 2.10 | 1.80 | 2.10 | 2.30 | 2.60 | 2.30 | 2.60 | 2.40 | 2.40 | 2.70 | 3 |
| 2005 | 1.60 | 1.60 | 1.80 | 1.80 | 2 | 2 | 2.40 | 2.30 | 2.50 | 2.30 | 2.20 | 1.90 |
| 2004 | 1.50 | 1.30 | 1.10 | 1.20 | 1.50 | 1.60 | 1.50 | 1.30 | 1.10 | 1.20 | 1.40 | 1.60 |
| 2003 | 1.40 | 1.60 | 1.60 | 1.50 | 1.20 | 1.10 | 1.20 | 1.30 | 1.50 | 1.50 | 1.30 | 1.30 |
| 2002 | 1.50 | 1.50 | 1.50 | 1.40 | 0.80 | 0.70 | 1.10 | 0.90 | 0.90 | 1.40 | 1.50 | 1.60 |
| 2001 | 1 | 0.70 | 1 | 1.10 | 1.60 | 1.60 | 1.50 | 1.90 | 1.40 | 1.10 | 0.80 | 1.10 |
| 2000 | 0.70 | 1 | 0.60 | 0.60 | 0.60 | 0.80 | 0.80 | 0.60 | 1 | 1.10 | 1.10 | 0.80 |
| 1999 | 1.60 | 1.40 | 1.70 | 1.50 | 1.40 | 1.40 | 1.30 | 1.30 | 1.30 | 1.10 | 1.10 | 1.10 |
| 1998 | 1.60 | 1.60 | 1.70 | 1.90 | 2 | 1.60 | 1.60 | 1.30 | 1.30 | 1.30 | 1.40 | 1.60 |
| 1997 | 2.10 | 1.90 | 1.60 | 1.60 | 1.60 | 1.70 | 1.90 | 2 | 1.90 | 1.90 | 1.90 | 1.70 |
| 1996 | 2.70 | 2.70 | 2.50 | 2.50 | 2.20 | 2.40 | 2.20 | 2.20 | 2.40 | 2.50 | 2.50 | 2.20 |
| 1995 | 2.30 | 2.30 | 2.60 | 2.30 | 2.40 | 2.40 | 2.60 | 2.60 | 2.90 | 2.90 | 2.90 | 3 |
| 1994 | 2.70 | 2.50 | 2.20 | 1.90 | 2 | 2 | 1.90 | 1.90 | 1.50 | 1.50 | 1.70 | 2 |
| 1993 | 2.30 | 2.40 | 2.60 | 2.60 | 2.50 | 2.50 | 2.60 | 2.90 | 3 | 2.50 | 2.40 | 2.40 |
| 1992 | 7 | 6.90 | 7.10 | 4.70 | 4.30 | 3.80 | 3.50 | 3 | 2.90 | 2.90 | 2.60 | 2.60 |
| 1991 | 7.10 | 6.90 | 6.80 | 8.50 | 8.30 | 8.40 | 8.40 | 8 | 7.20 | 6.80 | 7 | 7.10 |
| 1990 | 5.50 | 5.90 | 5.90 | 6.40 | 6.70 | 6.90 | 6.70 | 7.60 | 8.20 | 8.10 | 7.90 | 7.70 |
| 1989 | 5 | 4.90 | 5.10 | 5.30 | 5.50 | 5.20 | 5.20 | 5 | 5.20 | 5.60 | 5.50 | 5.50 |