number of seats and the portion of votes got by a party becomes less proportional). It is often regarded as the most important factor that limits the number of parties in Spain. This point is advanced when Baldini and Pappalardo compare it with the case of Netherlands, where the parliament is elected using proportional representation in a single national constituency. There, the parliament is much more fragmented and the number of parties is much higher than in Spain. The D'Hondt method (a type of highest average method) is used to allocate the seats, which slightly favors the major parties when compared to Sainte-Laguë method (another type of highest average method) or the normal kinds of largest remainder methods. It is suggested that the use of D'Hondt method also contribute to a certain degree, though not as large as the low number of seats per constituency, to the bipolarization of the party system. The 3% threshold for entering the Congress is ineffective in many provinces, where the number of seats per constituency is so low that the actual threshold to enter the Congress is effectively higher, and thus many parties cannot obtain representation in Congress despite having obtained more than the 3% threshold in the constituency. For example, the actual threshold for the constituencies having 3 seats is 25%, much higher than 3%, making the 3% threshold irrelevant. However, in the largest constituencies like Madrid and Barcelona, where the number of seats is much higher, the 3% threshold is still effective to eliminate the smallest parties. The size of the Congress (350 members) is relatively small. It is suggested by Lijphart that the small size of parliament may encourage disproportionality and so favor the large parties. Senate In the Senate, each province, with the exception of the islands, select four senators using block voting: voters cast ballots for three candidates, and the four senators with the greatest number of votes are selected. The number of senators selected for the islands varies, depending on their size, from 1 to 3 senators. A similar procedure of block voting is used to select the three senators from the three major islands whereas the senators of the smaller islands or group of islands, are elected by plurality. In addition, the legislative assembly of each autonomous community designates one senator, and another for each additional one million inhabitants. Electoral participation Electoral participation, which is not compulsory,