Erik Moberg ã:
A Theory of Democratic Politics
 
 

15.1 - THE CUBE RULE

In a majoritarian system the party getting most votes usually becomes over-represented in the legislature to a very considerable extent, and the party getting least votes is usually, and consequently, largely under-represented. The so called cube rule is the result of efforts to find a simple relationship, in a majoritarian system, between the quantities involved here. Originally it was formulated in 1909 by J. P. Smith in a report to the British Royal Commission on electoral systems. Let us assume that there are two parties which get V₁and V₂ votes in an election, counted nation-wide, and after that, using the plurality method, get M₁ and M₂ mandates respectively in the legislature. Then, according to the cube rule, (M₁ / M₂) = (V₁ / V₂)³. This rule has given a fairly good picture of the development in England during certain periods. For a further discussion of the cube rule see Duverger, 1964, p 322; and Rae, 1967, p 27. For later efforts to find formulas with a better fit than the cube rule see Blais & Massicotte, 1996, p 70.