The advantages of a strong-legislature model are many. From the standpoint of advancing democratization, the most important is the check placed on executive power. In polities with dominant legislatures, the most powerful executive is typically the prime minister. While prime ministers can be highhanded, they are usually more constrained than are presidents or monarchs. Prime ministers in parliamentary systems ultimately serve at the pleasure of their colleagues in parliament. They are less prone to democracy-endangering imperiousness than are executives who are not answerable to the legislature.
Over the past half-century, autonomous executives have been democracy's most obstinate foe. Even many figures with reputations as democrats who captured presidencies in free elections have subsequently abused their power and dragged their countries back toward authoritarianism. Russia's Boris Yeltsin, Peru's Alberto Fujimori, Kyrgyzstan's Askar Akayev, Zambia's Frederick Chiluba, and Kenya's Mwai Kibaki are examples.
In most developing countries, executives -- and particularly presidents -- enjoy a big advantage. Most agencies of state fall under their authority. Executives typically also shape the judiciary. The best hope for restraining the executive is a legislature that enjoys real clout.
In a recent study we investigated the effect of the power of the legislature vis-à-vis the executive on the fate of democratization around the world. We focus specifically on two questions: First, is the legislature free of executive appointees? When all legislators are elected, the legislature enjoys greater autonomy from the executive than when the executive appoints a portion (or all) of the legislature. Second, does the legislature alone make laws, or can the executive do so as well? If the executive can decree laws, the legislature must share its central function with the executive.
Drawing on a global survey of the powers of national legislatures, we coded countries in terms of whether their constitutions establish legislatures that are free of executive appointees and/or provide the legislature with a monopoly on legislating. We analyzed how these two provisions may affect countries' level of democracy. To assess democracy, we used data issued by Freedom House, adopting their categorization of countries as "free," "partly free," and "not free." We may label countries in the first category as democracies, those in the second as hybrid regimes, and those in the third as autocracies.