Though it may also be referred to as a charter or code, in most cases a constitution is the written plan of government for a given country. Within a nation's constitution are the fundamental principles and laws designed to govern the people, as well as the methodology and government structure by which the constitution is to be enforced, interpreted and changed.
A constitution provides a framework upon which all other laws and regulations of a government are to be based. It sets up the basic human structure of government and establishes how government officials are to be selected. When conflicting points of law appear, the constitution is the document appealed to by the judicial system to make a final decision.
Constitutions may be very stable, as in the case of the over-220-year-old Constitution of the United States, or they may be replaced on a fairly frequent basis. Thomas Ginsburg, Zachary Elkins and James Melton, in "The Lifespan of Written Constitutions," estimate that the average lifespan of a national constitution is about 17 years. More stable constitutions are preferable, as they make a country's actions more predictable. The stability of a constitution is determined first by the structure of the constitution and the state it governs, and second by the shocks and crises it must withstand. Poorly designed constitutions or constitutions that are unable to withstand wars, internal conflicts or disasters are likely to have short lifespans.