In the United States, we grow up thinking that it’s normal to have a two-party system, but this is more the exception than the rule around the world.  Most countries have 4-5 main political parties, and some have many more.  In this video, I describe three ways we evaluate party systems – the configuration of all political parties in a country – number, volatility, and polarization.


The number of parties that gain seats in parliament varies widely from country to country. When we talk about the number of parties in a country, we generally talk about which parties have seats in the legislature and we generally talk about the largest parties that have representatives.  For example, there are 10 parties with seats in the UK’s House of Commons, but only three of those have more than 5% of the seats. 

This number is determined both by the number of social cleavages in a country (such as class, ethnic, or religious differences) and by the country’s election laws (which I will discuss in a separate video).  There is no ideal number of parties – the “right” number is the number that reflect important groups and divisions in society. 

Countries that have a large number of political parties typically manage politics through coalitions.  There are two types of coalitions: pre-election coalitions and governing coalitions. 

Parties form pre-election coalitions when they want to remain as separate organizations, but run together with like-minded parties on a single candidate list.  Sometimes the reason for this is regional politics – for example, in Germany the Christian Democratic Union has a long-standing election coalition with the Christian Social Union, which operates only in the province of Bavaria while the CDU runs candidates in the rest of the country.  In other countries, election coalitions are a strategic move by smaller parties that want to make themselves more competitive.  For example, in Italy, parties tend to run as part of either a center-left or center-right election coalition.

When no single party gains a majority of seats in parliament in an election, the party with the most seats gets the first opportunity to form a coalition government.  That party will look to other parties that either share similar ideologies or have the right number of seats to form a majority in parliament.  These parties bargain for seats in the cabinet or policy concessions in exchange for their support for the government.  When margins are close, this can give a lot of leverage to small parties on the extreme right or left or small regional parties.

For example, from 2017-2019 in the UK, the Conservative Party did not have enough seats in parliament to govern on its own and formed a coalition with the Democratic Unionist Party, a unionist party based in Northern Ireland which had won 10 seats in the House of Commons, making issues related to the status of Northern Ireland particularly sensitive during Brexit talks. 

In most countries with many parties, governments will form larger coalitions so that the loss of one partner does not undermine the coalition.  For example, there are 30 parties with representatives in Brazil’s lower house of parliament (the Chamber of Deputies), but they have since formed a governing coalition (of 11 parties) and opposition coalition and independents.  Similarly, there are 27 parties represented in the Israeli Knesset, with 11 parties in the governing coalition.

Finally, some countries form what are called “Grand Coalitions” made up of the two (or more) largest vote-getters in parliament.  For example, in Germany, the Christian Democrats and Social Democrats have governed together through a grand coalition since 2013.


Volatility refers to the turnover of political parties – do the same parties run year after year (low volatility) or do new parties form for each election (high volatility)? 

High volatility is bad for democracy because it reduces accountability.  When different parties – which may simply reflect slightly different groups of the same politicians – run in each election, it is difficult to hold them responsible for their past actions, voting out people who performed poorly.

For example, Silvio Berluscioni ran as the head of Forza Italia starting in 1993, then formed a party called the People of Freedom in 2007, then reformed Forza Italia again in 2013.  Five of the 11 parties in the Italian parliament were founded in the past decade. 

Extremely low volatility can also be problematic for democracy, because it could indicate that new ideas and groups are not being integrated into the political system. 

Volatility tends to be extremely high in new democracies, as many new parties form and dissolve in rapid succession.  In some democracies, party systems become more stable over time.  For example, in Poland in 30 parties gained seats in parliament in the 1991 elections but just seven in the 2001 elections (with a clear majority for one party).  Having a smaller number of ideologically coherent parties tends to make it easier for voters to choose among them, but party system institutionalization of this kind is by no means guaranteed.


Finally, party systems can be evaluated based on the political opinions they represent.  This means ensuring that most political views are included in the system, but more commonly we look at how polarized a party system is – how far apart the ideological positions of parties are from each other.

Polarization is not a bad thing in moderation – without some degree of partisan identification and ideological difference, it is hard to tell parties apart from each other.  But polarization is on the rise around the world, reaching levels that in the past have led to the breakdown of democracy.

While we are familiar with this process in the United States, another example can be found in the Netherlands, where the platforms of parties have grown more and more ideologically distinct over time. This can also be shown in the 2017 election results, where the populist-nationalist Party for Freedom gained the second largest number of seats in parliament, and the Green party had the percent increase in seats since the last election.

Polarization contributed to the collapse of democracy in inter-war Europe, but that is not the only outcome of polarized politics. The United States, for example, has gone through broad cycles of rising and declining polarization over time.

As with the number of parties, both party system volatility and polarization both reflect public opinion (party identification is low in new democracies, for example) and shape it.  The exact cause of institutionalization or destabilization is an area of ongoing study.