Not all parliaments, of course, consist only of one chamber; many parliaments, particularly in larger countries, are bicameral, that is, composed of two chambers. Although there are wide variations between the various types of second chamber (also often known as an 'upper house' or a 'senate'), two generalizations about them can be made:
- Second chambers are generally less powerful than lower houses. Only occasionally are the two houses equally powerful. This is because second chambers often act as houses of review, rather than as a house of government.
- Because of this, second chambers are often smaller in size than the first chamber. Furthermore, second chambers are often designed to encompass different types of representation or different interest groups than are represented in the first chamber.
The most common use of second chambers is in federal systems, to represent the constituent units of the federation. For example, states in the USA (see US: Ethnic Minorities and Single-Member Districts) and Australia (see The Alternative Vote in Australia), Länder in Germany, and provinces in South Africa are all separately represented in an upper house. Typically, this involves a weighting in favour of the smaller states or provinces, as there tends to be an assumption of equality of representation. Another common type of alternative representation is the deliberate use of the second chamber to represent particular ethnic, linguistic, religious, or cultural groups. A second chamber may also deliberately contain representatives of civil society. In Malawi, for instance, the constitution provides for thirty-two of the eighty senators to be chosen by elected senators from a list of candidates nominated by social 'interest groups'. These groups are identified as women's organizations, the disabled, health and education groups, business and farming sectors, trade unions, eminent members of society, and religious leaders. The much-maligned British House of Lords is occasionally defended on the grounds that it contains individuals with specific policy expertise, who can check the government legislation drawn up by generalist politicians.
Because of these variations, many second chambers are either partly elected, indirectly elected, or not elected. Of those that are elected, most jurisdictions have chosen to reflect the different roles of the two houses by using a different electoral system for their upper house to that which they use for their lower house. In Australia, for example, the lower house is elected by a majoritarian system (AV - see Alternative Vote), while the upper house, which represents the various states, is elected using a proportional system (STV see Single Transferable Vote). This has meant that minority interests who would normally be unable to win election to the lower house still have a chance of gaining election, in the context of state representation, in the upper house.
