The idea that checks and balances in the government—such as legislative oversight of the executive branch—can reduce corruption is intuitive, but quantitative empirical evidence for or against this hypothesis is relatively scant. Moreover, the effect of a separation of powers on the extent of corruption may depend on whether the same political party or faction controls both branches of government, or whether different factions control the legislature and the executive. Indeed, some legal scholars have argued that the true separation of powers is not between branches of government, but rather the political parties in the government, and that the traditional view of the separation of powers—ambition counteracting ambition—only works if different branches are controlled by different political parties. But the likely effect of such partisan separation on corruption is not entirely clear: If the legislature is controlled by a party or coalition opposed to the party that controls the executive branch, this could mean increased legislative oversight and lower corruption, but alternatively, increased opposition may simply drive the executive to bribe the opposition to go along with his or her agenda, leading to more corruption.

Carlos Varjão and I investigate this the question empirically in our recent working paper, “Political Opposition, Legislative Oversight, and the Performance of the Executive Branch.” We focus on municipal governments in Brazil, which are particularly suitable for this sort of study for a number of reasons: there are many municipalities with a similar overall government structure, there’s a wealth of data on various forms of corruption (mainly embezzlement, procurement fraud, and over-invoicing) from Brazil’s public audit reports, and there’s considerable variation in both the level of corruption and the political control of the branches of the municipal governments. Our findings are striking and unambiguous: increased representation of the political opposition in the local legislature is associated with more legislative oversight of the executive, less executive branch corruption, and better public service delivery. Continue reading →