A coalition government is a form of government in which political parties cooperate to form a government. The usual reason for such an arrangement is that no single party has achieved an absolute majority after an election, an atypical outcome in nations with majoritarian electoral systems, but common under proportional representation. A coalition government might also be created in a time of national difficulty or crisis (for example, during wartime or economic crisis) to give a government the high degree of perceived political legitimacy or collective identity, it can also play a role in diminishing internal political strife. In such times, parties have formed all-party coalitions (national unity governments, grand coalitions). If a coalition collapses, the Prime Minister and cabinet may be ousted by a vote of no confidence, call snap elections, form a new majority coalition, or continue as a minority government.