6 Suggestions for further research

So far, we have attempted to make some sense of where aggregation is present and where it is lacking in the EU arena. But this only raises two further questions. The first is one of causation, the second one of constraint. The question of causation is: where aggregation seems to work, well, how far can that be attributed to party politics at the Union level? The question of constraint is: where aggregation seems to be lacking, why do parties not develop further in the EU arena to fill the gap? Compared with matters considered so far, these two new questions take us on to more treacherous ground, where existing research allows us to form plausible hypotheses without always generating the evidence needed to adjudicate between them. As such, this section is more suggestive than previous ones of where further investigation is needed. For the sake of brevity, the question of causation is examined through the example of the groups in the EP, and that of constraint through an analysis of why European Union parties are absent from the electoral arena.

6.1 Causation?
6.2 Constraint