Parliamentary republics have separated the roles of head of state  and head of government. They are thus quite  similar to parliamentary monarchies, but the head of state is an elected president rather than a king or queen. Parliamentary constitutions are based on the premise that all power emanates from the people, and that the power is vested in their elected representatives in congress between the elections – just like the shareholders of a corporation elect a board of directors to manage business between the annual meetings.

Parliamentary constitutions are based on the principle of the sovereignty of the people, whereas presidential republics are based on the principle of separation of powers.

In practice this means that the government is dependent on the support of the congress, since the congress has the power to dismiss the head of government (and thus all of his cabinet). While in a presidential republic it would take a recall vote to depose the president (and thus all of his cabinet) for political reasons, in a parliamentary republic the cabinet can be dismissed by a vote in the parliament on short notice. This gives more political control over the government, and gives a voice to a larger segment of society.

The parliamentarians are elected in such a way as to represent the full range of diversity in the country, and proportional to the actual situation in the electorate. This is important; there cannot be one-person districts, because if so, a large percentage of the constituents may end up lacking representation. How large? Well over 50%, perhaps up to 67% or so, thanks to gerrymandering. If one third rules over two thirds, is that democracy? In a parliamentarian system with proportional representation, all parties larger than some 5% of the electorate can be represented in the parliament in proportion to their actual support.

A president only needs 50.01% of the electorate to win, and less if the vote counting is not proportional (as in the USA). Furthermore, presidential republics tend to be two party systems, just one up from one party systems. Thus, to buy the presidency it is enough to buy two candidates. It is self-evident that it is much harder to buy the government in a parliamentarian system, since you would have to buy the support of a majority of the congressmen.

Empirical Evidence

In a report from the World Bank titled “Accountability and Corruption – Political Institutions Matter” (World Bank Policy Research Working Paper No. 2708, 2001) the authors conclude that:

“The main results show that political institutions seem to be extremely important in determining the prevalence of corruption. In short, democracies, parliamentary systems, political stability, and freedom of press are all associated with lower corruption. Additionally, we show that common results of the previous empirical literature on the determinants of corruption – related to openness and legal tradition – do not hold once political variables are taken into account.” (my emphasis)

Also the political stability is higher in parliamentary systems. In How Democratic is the American Constitution? (2001), Robert A. Dahl writes that since 1950, only 22 nations have managed to remain stable with no coups or other discontinuity of the constitutional order. Of those 22, only 2 are presidential republics (USA and Costa Rica). The remaining 20 are parliamentary, 11 republics and 9 monarchies.

As for rule of law, see a previous post on Rule of Law Index 2010.

There is thus empirical evidence that parliamentary democracies:

• offer better protection against coup d’états
• foster less corruption
• foster more rule of law