| SIF data source | SIF2009 | SIF2014 | SIF2015 | |
| N (case files) | 360 | 629 | 503 | |
| Mean (samples/case file) | 14.72 | 13.31 | 12.03 | |
| Median | 3 | 3 | 3 | |
| Mode | 1 | 3 | 3 | |
| Std. Deviation | 34.17 | 44.35 | 36.13 | |
| Skewness | 5.68 | 7.48 | 7.08 | |
| Kurtosis | 41.18 | 73.42 | 63.41 | |
| Minimum | 1 | 1 | 1 | |
| Maximum | 343 | 618 | 400 | |
| Total number of samples | 5300 | 8370 | 6073 | |
| Mean | 14.72 | 13.31 | 12.03 | |
| Percentiles | 25% | 1 | 2 | 2 |
| 50% | 3 | 3 | 3 | |
| 75% | 14 | 4.5 | 5 | |