Democracy isn't just good for political rights — it's good for public health. A recent paper, written by Princeton economist Thomas Fujiwara, found that, when Brazil made it easier for poor people to vote, the percentage of Brazilian babies born at low birth weight (a strong predictor of infant mortality) declined. In other words, expanding voting rights made babies healthier.

Here's a brief explanation of he demonstrated that — and why you should care about the results. (Hat tip to Columbia professor Chris Blattman.)

What the study finds

When Brazil introduced electronic voting, poor voters had an easier time voting and voted in higher numbers. They overwhelmingly supported left-wing parties, who increased spending on public health care for their poorer constituencies needed it. More robust public health care services led to more mothers seeing doctors, thus reducing the number of babies born at low birth weight.

Until 1994 Brazil's elections were done by paper ballot only. These ballots were designed somewhat confusingly, and were also basically useless for illiterate voters. So despite the fact that Brazil has compulsory voting, uneducated voters, who tended to be poorer, often ended up turning in incomplete or incorrectly filled out ballots.

Brazil's new electronic voting systems use screens showing pictures of candidates, have simpler interfaces, and use numbers (like ATM machines) instead of words whenever possible. That made it considerably easier to vote.

It really seems like Fujiwara is onto something

Fujiwara tracked the effect, state-by-Brazilian state, of these new ballot systems on elections. He found that, in areas with electronic ballots were, poor voters filled out more ballots correctly.

These newly enfranchised voters voted for left wing parties that now had an incentive to prioritize public health care, which is a major issue for their lower-income voters. Fujiwara found correlations between the introduction of electronic voting and increases in public health funding, increases in the number mothers getting prenatal health care, and declines in the number of low-weight babies born. These correlations were statistically robust, and survived tests for confounding explanations.

Why it matters

In a certain sense, it's obvious why it matters: public health is improving in Brazil, thanks in part to electronic voting. That's a good thing for Brazilians!

But this also reinforces how important full voter access is. People from different income brackets often tend to vote differently — check out these maps of US voting by income below, by Andrew Gelman of FiveThirtyEight. Increasing access to voting for lower-income citizens, then, isn't just about getting more people to the polls, it's about full democratic representation.

Fujiwara's research also suggests that expanding democracy is a really good way to further the interests of the poor. Democracy makes governments responsive to the needs of their peoples. Brazil's poorest citizens used democracy to shape the government to fit to their material needs. It's a lessons for all democracies, not just Brazil.