Bicameralism
A legislature divided into two separate assemblies or houses.
Bicameralism is a system of government where the legislature is split into two separate chambers or houses. This differs from unicameralism, in which all lawmakers meet and vote together. As of 2022, about 60% of national legislatures around the world are bicameral, while 40% are unicameral; the unicameral model is even more common at the subnational level. After a decline in the early 1900s, the number of bicameral legislatures has grown significantly since the 1970s.
The two chambers are often chosen through different methods of election or selection, which can vary by country. This frequently results in the two houses having very different membership compositions. For a law to be enacted, a concurrent majority—approval from a majority in both chambers—is often required. When this is the case, the system is called perfect bicameralism. However, in many parliamentary and semi-presidential systems, the house that the executive answers to (like the UK’s House of Commons or France’s National Assembly) can overrule the other house (such as the UK’s House of Lords or France’s Senate). This is known as imperfect bicameralism. Some legislatures fall in between, where one house can override the other only under specific conditions.
The British Parliament is often called the "Mother of Parliaments," though this is a misquote of John Bright, who said in 1865 that "England is the Mother of Parliaments." It has served as the model for most other parliamentary systems, and its Acts have created many other parliaments. British bicameralism began in 1341, when the Commons first met separately from the nobility and clergy, forming an Upper Chamber and a Lower Chamber. The knights and burgesses sat in the Lower Chamber. The Upper Chamber became known as the House of Lords from 1544 onward, and the Lower Chamber became the House of Commons; together they are called the Houses of Parliament.
The Founding Fathers of the United States also supported a bicameral legislature. They wanted the upper chamber, the Senate, to be appointed by state legislatures, unlike the lower House of Representatives. Benjamin Rush noted that "this type of dominion is almost always connected with opulence." The Senate was meant to be a stabilizing force—not elected by the general public, but chosen by state legislators.
- Type
- Legislative system
- Percentage of national legislatures 2022
- ~60%
- Percentage of national unicameral legisl
- ~40%
- Trend since 1970s
- Increased significantly
- Trend early 20th century
- Decline
- Key example origin
- British Parliament (1341)
Lore & Background
The British Parliament is often referred to as the 'Mother of Parliaments' because it has been the model for most other parliamentary systems. The origins of British bicameralism trace to 1341, when the Commons met separately from the nobility and clergy, creating an Upper Chamber and a Lower Chamber. The Upper Chamber became known as the House of Lords from 1544 onward, and the Lower Chamber became the House of Commons.
The Founding Fathers of the United States favored a bicameral legislature, with the Senate appointed by state legislatures and the House of Representatives elected by popular vote. James Madison argued the Senate would provide 'more coolness, more system and more wisdom' than the popular branch. As part of the Connecticut Compromise, the Senate would have equal representation from each state. Notably, the last formal free conference between the two houses of the British Parliament occurred in 1740, not 1836 as sometimes mistakenly reported.
Reader's Guide
Bicameralism is significant as a foundational structure for many national legislatures, particularly in federal systems. It provides a mechanism for checks and balances, with proponents arguing it helps prevent ill-considered legislation, while critics believe it makes meaningful political reforms more difficult and increases gridlock. The relationship between the two chambers varies: in some cases they have equal power (common in federal and presidential systems), while in others one chamber is clearly superior (common in unitary parliamentary systems). Enactment of primary legislation often requires a concurrent majority—approval of a majority in each chamber—known as perfect bicameralism. However, in many parliamentary and semi-presidential systems, the house to which the executive is responsible can overrule the other house, an example of imperfect bicameralism. Formal communication between houses includes sending messages, transmission of bills, joint sessions, joint committees, and conferences. The British Parliament's bicameral model has influenced many other parliaments, and the United States' federal bicameral system has been widely emulated. As of 2022, roughly 40% of national legislatures are bicameral, a proportion that has increased since the 1970s.
Did You Know?
- As of 2022, roughly 40% of the world's national legislatures are bicameral.
- The United States Senate was originally appointed by state legislatures, not elected by popular vote, until the 17th amendment in 1913.
- Formal communication between houses can include joint sessions, joint committees, and conferences, with the last free conference at Westminster occurring in 1836.
Frequently Asked Questions
What is bicameralism?
Bicameralism is a legislative arrangement in which a country's lawmaking body is split into two distinct chambers or houses rather than a single assembly. Each chamber typically has its own membership, procedures, and sometimes different powers.
How does bicameralism differ from unicameralism?
In a unicameral system all legislators sit together in one chamber to debate and vote, while bicameralism divides that role across two separate bodies. The two houses often use different methods for selecting their members, adding an extra layer of deliberation before a bill passes.
How widespread is bicameralism today?
As of 2022, roughly 60 percent of national legislatures worldwide operate on a two-house model, leaving about 40 percent unicameral. The unicameral approach is even more common at the subnational level, and the number of bicameral systems has grown significantly since the 1970s after an early twentieth-century decline.
Where did bicameralism first appear?
The British Parliament is widely regarded as the key historical origin of the modern bicameral model, with its two-house structure taking shape around 1341. Many subsequent national legislatures modeled their upper and lower chambers on that English precedent.
Why do governments adopt bicameralism?
Splitting the legislature into two chambers provides a second, independent check on legislation before it becomes law. The differing selection methods and compositions of each house can represent different interests—such as regions versus the population at large—making the overall process more deliberative.
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