the Spanish parliament recently. Comparisons with other party systems Two-party systems can be contrasted with: Multi-party systems. In these, the effective number of parties is greater than two but usually fewer than five; in a two-party system, the effective number of parties is two (according to one analysis, the actual average number of parties varies between 1.7 and 2.1). The parties in a multi-party system can control government separately or as a coalition; in a two-party system, however, coalition governments rarely form. Examples of nations with multi-party systems include Brazil, Canada, Denmark, Finland, France, Germany, India, Pakistan, Indonesia, Ireland, Israel, Italy, Mexico, Nepal, the Netherlands, Belgium, New Zealand, Norway, Philippines, Portugal, Ukraine, Spain, Sweden and Thailand. Dominant-party systems are present in countries, which are formally democratic, but a dominant party hold a vast majority for decades and the party institutions are partially molten with the major institutions of the state. Unlike in one-party-states, civil rights and freedom of press are at least partly preserved. Examples for this type are the People's Action Party of Singapore, the South African National Congress, the SWAPO in Namibia, and United Russia in Russia. One-party systems happen in nations where no more than one party is codified in law and/or officially recognized, or where alternate parties are restricted by the dominant party which wields power. Examples include rule by the Communist Party of China, Communist Party of Vietnam, and Communist Party of Cuba. Causes There are several reasons why, in some systems, two major parties dominate the political landscape. There has been speculation that a two-party system arose in the United States from early political battling between the federalists and anti-federalists in the first few decades after the ratification of the Constitution, according to several views. In addition, there has been more speculation that the winner-takes-all electoral system as well as particular state and federal laws regarding voting procedures helped to cause a two-party system. Political scientists such as Maurice Duverger and William H. Riker claim that there are strong correlations between voting rules and type of party system. Jeffrey D. Sachs agreed that there was a link between voting arrangements and the effective number of parties. Sachs explained how the first-past-the-post voting arrangement tended to promote a two-party system: Consider a system in which voters can vote for any candidate from any one of many parties. Suppose further that if a party gets 15%