by Maurice Y. Michaud (he/him)
There’s an old saying that when the numbers look too good to be true, somebody must’ve “cooked the books” in order to make them come out that way. This search engine aims to prove that the math doesn’t lie: Scotland’s formula for seat distribution in its legislative assembly has an almost uncanny ability to achieve remarkable proportionality on its own mathematical merits, even without adding any extra or “overhang” seats as is done over there to reach a perfect balance. And for proof, one only needs to compare some past results through the lens of the Gallagher index, or GI.
The GI gives us an easy-to-grasp number from 0 to 100. Below 5, the outcome was relatively proportional. Below 2, the outcome was very proportional. Above 5, however, some distortion was becoming apparent. And anything above 10, we could speak only of disproportionality.
The line graphic for each jurisdiction, to which you can gain access through this search engine, helps to explain why Germany and New Zealand require so many overhang seats, while the pure methods, although they tend to improve the outcome, fall short when dealing with real-life numbers. While the relative stability and predictability of the Scottish model seems almost too good to be true, remember: this is applied mathematics using real, verified data. Even with complicated result sets, the Scottish model almost always manages to keep the GI below 10 and often very near or below 5.
