A histogram of small, medium and large active regions where, within each group, each column block represents a different active region type For example, the grey blocks are eruptive sigmoids and the hatched blocks are eruptive non-sigmoids. It can be seen from this that, for all sized of region, sigmoidal regions are more likely to erupt than non-sigmoidal regions, and that there are not very many sigmoidal regions which do not erupt (white). From Canfield, Hudson & McKenzie 1999, Geophys.Res.Lett. 26, p627