Voters in this weekend’s elections in Uruguay and Brazil have something in common: They are legally required to cast a ballot. Both countries have compulsory voting, under which failure to vote is punishable by a fine. Roughly 30 countries, and nearly a fifth of electoral democracies, have some form of national compulsory voting law on the books, though only some of these laws are enforced. And of these countries, 13 of them are in Latin America.

With compulsory voting laws in about half of its countries, Latin America has by far the highest concentration of such laws on any continent. “It’s been a contentious and hotly debated question,” Michael Shifter, president of the Inter-American Dialogue, an organization focused on Western Hemisphere affairs, told me by email. “Advocates believe a full democracy needs to respond to the views and interests of all citizens. ... Of course, the chief argument against compulsory voting is that it contradicts the freedom associated with democracy.”

These kinds of arguments are presumably applicable all over the world, so why is compulsory voting so prevalent in Latin America specifically?

Compulsory Voting Around the World

Countries with nationwide compulsory voting laws. (Created with Datawrapper. Data: International Institute for Democracy and Electoral Assistance)

In a 2010 paper, Gretchen Helmke and Bonnie Meguid of the University of Rochester investigated the origins of compulsory voting laws and the factors that could motivate a ruling party to adopt them. Comparing countries that instituted mandatory voting laws with a random sample of countries that didn’t, they found support for the theory that “the more incumbents fear that they are losing the ability to get their own voters to the polls, the more appealing an antidote compulsory voting will be. In essence, the decision to adopt [compulsory voting] is based on the incumbent’s wager that abstaining voters are the equivalent of untapped supporters.”

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Ruling parties in Western European and Latin American countries, the authors write, faced the rise of unions and workers’ parties as their countries industrialized during the late 1800s and early 1900s, when many of them implemented their compulsory voting laws. “During this period, the Left’s organizational ability to mobilize—and, in particular, turn out—its potential voters was increasingly perceived as being unmatched by other parties,” they write. Ruling parties, according to this theory, were essentially trying to get out the vote for a silent majority of what one Argentine official called “the rich and content” to protect their incumbency from the growing power of the leftist opposition.

Brazil, Ecuador, Paraguay, Uruguay, and Peru all passed compulsory voting laws in the 1930s. Each later went through a period of military dictatorship between the 1950s and the 1980s. When democracy returned, so did the requirement to vote.