What Is a Unicameral System?

A unicameral system is a government with one legislative house or chamber. Unicameral is the Latin word that describes a single-house legislative system. Countries with unicameral governments include Armenia, Bulgaria, Denmark, Hungary, Monaco, Ukraine, Serbia, Turkey, and Sweden. Unicameral systems became more popular during the 20th century and some countries, including Greece, New Zealand, and Peru, switched from a bicameral to a unicameral system.

Smaller countries with long-established democracies tend to have unicameral systems while larger countries may have either a unicameral or bicameral system.

Understanding a Unicameral System

To understand how a unicameral system works, consider the national government of Sweden. Sweden has a parliamentary system with a king as the formal head of the country and the prime minister serving as the seat of executive power. There are 349 seats in the Parliament and any political party that receives at least 4% of the vote during the national vote is granted seats. The number of seats each party receives is based on the number of votes received and proportional representation by electoral district. In 2020, , led by the Social Democrats with 100 seats, or 28.7%, and closely followed by the Moderates, with 70 seats, or about 20.1%. The Green Party and the Independents had the smallest share at 4.6% and 0.6% seats, respectively. Parliament votes on legislative bills, which are proposed by Members of Parliament (MPs) or by government. All bills except the budget and changes to the Constitution are approved by a simple majority vote of the Parliament. Parliament also approves the prime minister. The Parliament meets annually and elections are held every four years. Neither the prime minister nor MPs have term limits.

Advantages of a Unicameral vs. Bicameral System

While the major advantage of a bicameral system is that it can provide for checks and balances and prevent potential abuses of power, it can also lead to gridlock that makes the passage of laws difficult. A major advantage of a unicameral system is that laws can be passed more efficiently. A unicameral system may be able to pass legislation too easily, however, and a proposed law that the ruling class supports may be passed even if the majority of citizens do not support it. Special interest groups may influence a unicameral legislature more easily than a bicameral one, and groupthink may be more likely to occur. Because unicameral systems require fewer legislators than bicameral systems, however, they may require less money to operate. These systems may also introduce fewer bills and have shorter legislative sessions.

A unicameral system for the U.S. government was proposed by the Articles of Confederation in 1781, but the delegates to the Constitutional Convention in 1787 created a plan for a bicameral system that was modeled on the English system. America’s founders could not agree on whether the states should each have the same number of representatives or whether the number of representatives should be based on population. The founders decided to do both in an agreement known as the Great Compromise, establishing the bicameral system of the Senate and the House that we still use today. The U.S. federal government and all the states except Nebraska use a bicameral system while U.S. cities, counties, and school districts commonly use the unicameral system, as do all the Canadian provinces. Initially, Georgia, Pennsylvania, and Vermont had unicameral legislatures based on the idea that a true democracy should not have two houses representing an upper class and a common class. Instead, a democracy should have single house representing all people. Each of these states turned to a bicameral system: Georgia in 1789, Pennsylvania in 1790, and Vermont in 1836. Similar to the United States, Australia also has just one state with a unicameral system: Queensland.

A Republican named George Norris successfully campaigned to change Nebraska’s legislature from a bicameral to a unicameral system in 1937. Norris claimed that the bicameral system was outdated, inefficient, and unnecessary. Norris said a unicameral system could maintain a system of checks and balances by relying on the power of citizens to vote and petition and by relying on the Supreme Court and the governor on matters that required another opinion. Further, a bill may only contain one subject and may not pass until five days after its introduction. Most Nebraska bills also receive a public hearing and each bill must be voted on separately three times.

Some countries with unicameral systems have always held such a system while others have changed at some point by merging two houses or abolishing one. New Zealand abolished its upper house in the early 1950s when the Opposition party took control from the Labour party and voted to do away with the upper house.