suggested that third parties arose from time to time in the nineteenth century around single-issue movements such as abolition, women's suffrage, and the direct election of senators, but were less prominent in the twentieth century. A so-called third party in the United Kingdom were historically the Liberal Democrats, prior to the Scottish National Party taken its place since the 2015 election by number of the House of Common seats. In the 2010 election, the Liberal Democrats received 23% of the votes but only 9% of the seats in the House of Commons. While electoral results do not necessarily translate into legislative seats, the Liberal Democrats can exert influence if there is a situation such as a hung parliament. In this instance, neither of the two main parties (at present, the Conservative Party and the Labour Party) have sufficient authority to run the government. Accordingly, the Liberal Democrats can in theory exert tremendous influence in such a situation since they can ally with one of the two main parties to form a coalition. This happened in the Coalition government of 2010. More than 13% of the seats in the British House of Commons are held in 2011 by representatives of political parties other than the two leading political parties of that nation, such that contemporary Britain is considered by some to be a multi-party system, and not a two-party system. The two party system in the United Kingdom allows for other parties to exist, although the main two parties tend to dominate politics; in this arrangement, other parties are not excluded and can win seats in Parliament. In contrast, the two party system in the United States has been described as a duopoly or an enforced two-party system, such that politics is almost entirely dominated by either the Republicans or Democrats, and third parties rarely win seats in Congress. Advantages Some historians have suggested that two-party systems promote centrism and encourage political parties to find common positions which appeal to wide swaths of the electorate. It can lead to political stability which leads, in turn, to economic growth. Historian Patrick Allitt of the Teaching Company suggested that it is difficult to overestimate the long-term economic benefits of political stability. Sometimes two-party systems have been seen as preferable to multi-party systems because they are simpler to govern, with less fractiousness and greater harmony, since it discourages radical minor parties, while multi-party systems