readme: add some dataset stats

README.md

@@ -81,7 +81,7 @@ sogleich	O	_
 
 Note: we include a `-DOCSTART-` marker to e.g. allow document-level features for NER as proposed in the [FLERT](https://arxiv.org/abs/2011.06993) paper.
 
-## Dataset Splits
+## Dataset Splits & Stats
 
 For training powerful NER models on the dataset, we manually document-splitted the dataset into training, development and test splits.
 
@@ -89,6 +89,20 @@ The training split consists of 73 documents, development split of 13 documents a
 
 We perform dehyphenation as one and only preprocessing step. The final dataset splits can be found in the `splits` folder of this dataset repository.
 
+Some dataset statistics - instances per class:
+
+| Class | Training | Development | Test |
+| ----- | -------- | ----------- | ---- |
+| `PER` | 942      | 308         | 238  |
+| `LOC` | 749      | 217         | 216  |
+| `ORG` | 16       |   3         | 11   |
+
+Number of sentences (incl. document marker) per split:
+
+|           | Training | Development | Test |
+| --------- | -------- | ----------- | ---- |
+| Sentences | 1.539    | 406         | 400
+
 # Release Cycles
 
 We plan to release new updated versions of this dataset on a regular basis (e.g. monthly).