Unicameralism is the practice of having only one legislative or parliamentary chamber. Many countries with unicameral legislatures are often small and homogeneous unitary states and consider an upper house or second chamber unnecessary.
Supporters of unicameralism note the need to control government spending and the elimination of redundant work done by both chambers. Critics of unicameralism point out the double checks and balances that a bicameral system affords, forcing a greater level of consensus on legislative issues. A feature of unicameralism is that urban areas with large populations have more influence than sparsely populated rural ones. In many cases the only way to get sparsely populated regions on board a unified government is to implement a unicameral system (such as the early United States). Supporters say this is an advantage, as they see it provides better apportionment while opponents see giving more power to rural regions as a goal in itself.
Unicameral legislatures were and are also common in Communist (like People's Republic of Poland, People's Republic of China and Cuba) and former Communist states (like Ukraine, Moldova and Serbia), since under Socialist point of view the institution of Senate was seen as conservative, oligarchial, elitist and pro-bourgeoise by nature.
Some of the subnational entities with unicameral legislatures include Nebraska, Guam and the Virgin Islands in the United States, Hong Kong, the Australian states and territories of Queensland, Northern Territory and the Australian Capital Territory, all of the provinces and territories in Canada, all of the German Bundesländer, all of the Italian Regioni.
Virtually all city legislatures are also unicameral in the sense that the city councils are not divided into two chambers. Until the turn of the 20th century, bicameral city councils were common in the United States.
In a non-binding referendum held on July 10, 2004, voters in the U.S. territory of Puerto Rico approved changing its Legislative Assembly to a unicameral body by 456,267 votes in favor (83.7%) versus 88,720 against (16.3%). If both the territory's House of Representatives and Senate approve by a 2/3 vote the specific amendments to the Puerto Rico Constitution that are required for the change to a unicameral legislature, another referendum will be held in the territory to approve such amendments. If those constitutional changes are approved, Puerto Rico will switch to a unicameral legislature as early as 2009.
Local government legislatures of counties, cities, or other political subdivisions within states are usually unicameral and have limited lawmaking powers compared to their state and federal counterparts.