The advantages of a bicameral legislature include stability, more varied representation and the passing of quality legislation. The disadvantages include deadlock and unequal representation. A majority of the countries in the world have bicameral legislatures.
The stability of a bicameral legislative system comes from the ability of the two houses to check each other's power. This prevents a dictatorship of the majority and avoids the passing of legislation based merely on popularity. The houses in a bicameral legislature are typically elected or selected through different processes, allowing for more versatility and forms of representation. In the United States, for instance, members of the House of Representatives are elected in district elections every two years, while members of the Senate are elected in state-wide elections every six years. Because the process in such a legislative system is slower, it forces quality decision-making and compromise that is often not seen in unicameral legislatures.
Bicameral legislatures do have their disadvantages, however, among the primary of which is deadlock, or an inability to pass legislation because neither house is willing to budge on its version of a bill. Bicameral parliaments also often have houses whose members wield equal voting power, although they may represent a significantly different number of voters. In the United States, for instance, the most populous and least populous state have the same number of senators.