| Year | Real | Predictions | Relative error | Level ratio |
| 2008 | 5.24 | 5.24 | 0.00% | 0.00 |
| 2009 | 4.36 | 4.54 | −4.13% | −0.085 |
| 2010 | −2.33 | −2.12 | 9.01% | 0.024 |
| 2011 | −3.46 | −3.27 | 5.49% | −0.054 |
| 2012 | 4.29 | 3.98 | 7.23% | 0.084 |
| 2013 | 3.68 | 3.45 | 6.25% | 0.054 |
| 2014 | 2.85 | 2.97 | −4.21% | 0.043 |
| 2015 | 1.86 | 2.04 | −9.68% | −0.074 |
| 2016 | 4.82 | 4.54 | 5.81% | 0.026 |
| 2017 | −2.24 | −2.44 | −8.93% | −0.083 |
| 2018 | −0.56 | −0.52 | 7.14% | −0.036 |
| 2019 | −1.95 | −1.76 | 9.74% | 0.067 |
| 2020 | 4.7 | 4.55 | 3.19% | 0.086 |