[Ari_Rahikkala]

AIT applies to:

- Votes with at least three options. A simple majority vote between two options does in fact satisfy all of Arrow's fairness criteria (if only vacuously).

- Ranked voting systems, i.e. ones where voters only give a rank ordering of their options, not any more information.

Quadratic voting is neither of those: It applies only to binary decisions, but for those decisions, it tries to be more fair than Arrow's criteria call for, by getting out not only information about which option voters prefer, but how strongly they prefer it. Whether it could be extended to more complex votes than binary ones, I don't know.