Qualified majority voting : the effect of the quota

We explore the effect of various values of the quota of QMV in an enlarged, 27-member Council of Ministers of the EU. In order to isolate the effect of the quota q, we assume, for all values of q, an ‘equitable’ distribution of voting power, according to Penrose’s Square-Root Rule. For each value of q from q = 51% to near 100% of the total weight, we compute the system of weights that produces an equitable distribution of voting power. This enables us to examine the effect of q (with an equitable distribution of power) on various quantities, including: the voting power of each member; the blocking power (Coleman’s ‘power to prevent action’) of each member; the sensitivity of the decision rule; Coleman’s parameter A (‘ability of the collectivity to act’); the mean majority deficit. A particularly interesting phenomenon is the effect of varying q on the weight of each member.