Why are Brazil’s presidential polls so different from one another?

. Jun 28, 2018
Brazil's presidential polls Brazil's presidential polls are at the center of a controversy
Brazil's presidential polls

Presidential polls are at the center of a controversy

At the beginning of June, a presidential poll by DataPoder360 – a company created by news website Poder360 –  created havoc in financial markets. It showed the election front-runners to be two candidates dreaded by investors: the far-right Jair Bolsonaro, who had a comfortable lead with 25 percent of voting intentions, and the center-left Ciro Gomes, with 12 percent. São Paulo’s stock market crashed by 6 percent, and the Brazilian Real lost 2 percent against the U.S. Dollar, which closed June 7 at BRL 3.95. 

datapoder360 Brazil's presidential polls

Three days later, Datafolha &#8211; Brazil&#8217;s most renowned polling institute &#8211; published its own poll, with different numbers. While Mr. Bolsonaro was also leading in all scenarios that exclude former President Luiz Inácio Lula da Silva (currently in jail and unlikely to be able to run for a third term), his numbers were much lower, around 19 percent. </span></p> <hr /> <p><img loading="lazy" class="alignnone size-large wp-image-5391" src="" alt="datafolha Brazil's presidential polls" width="1024" height="590" srcset=" 1024w, 300w, 768w, 610w, 1180w" sizes="(max-width: 1024px) 100vw, 1024px" /></p> <hr /> <p><span style="font-weight: 400;">A third institute, Ipespe, was hired by an investment bank to hold presidential polls which targeted investors &#8211; and threw up another set of results. In scenarios where Lula is considered as a candidate, Mr. Bolsonaro narrowed the gap &#8211; and the poll even places him in a better position than Lula in a head-to-head second round contest (although technically in a tie). It was the first time this had occurred.</span></p> <hr /> <p><img loading="lazy" class="alignnone size-large wp-image-5394" src="" alt="ipespe Brazil's presidential polls" width="1024" height="434" srcset=" 1024w, 300w, 768w, 610w, 1180w" sizes="(max-width: 1024px) 100vw, 1024px" /></p> <p><img loading="lazy" class="alignnone size-large wp-image-5411" src="" alt="ipespe Brazil's presidential polls second round runoff stage" width="1024" height="337" srcset=" 1024w, 300w, 768w, 610w, 1180w" sizes="(max-width: 1024px) 100vw, 1024px" /></p> <hr /> <p><span style="font-weight: 400;">While the candidates and the voters are the same, the three institutes gave three very different depictions of the electoral landscape. So, who should you trust: Datafolha or its competitors (Ipespe and DataPoder360)?</span></p> <p><span style="font-weight: 400;">The main difference between Datafolha and the other two is methodological: Datafolha conducts face-to-face interviews, while others run telephone surveys (often with automated calls), which are quicker and less expensive. </span></p> <h3>The argument in favor of telephone polls</h3> <p><span style="font-weight: 400;">Jair Bolsonaro is polling better on telephone surveys. Defenders of this methodology say it&#8217;s because voters are more prone to give their opinion over the phone, without fear of being judged as extremists. Mr. Bolsonaro, after all, is frequently associated with homophobic, racist, and misogynist views. </span></p> <p><span style="font-weight: 400;">Political scientist Antonio Lavareda, the CEO of Ipespe, defends his methods. He told <strong>The Brazilian Report </strong>that traditional polling institutes &#8220;discredit telephone polls to keep a market reserve for face-to-face polling, a very expensive method.&#8221;</span></p> <p><span style="font-weight: 400;">Even if telephone polls can indeed over-represent some segments of society &#8211; and under-represent others &#8211; there are statistical methods to correct that bias. In an article called </span><a href=""><span style="font-weight: 400;">&#8220;</span><i><span style="font-weight: 400;">Forecasting elections with non-representative polls,&#8221;</span></i></a><span style="font-weight: 400;"> authors Wei Wang, David Rothschild, Sharad Goel, and Andrew Gelman used a poll conducted on the Xbox gaming console to correctly predict the results for the 2012 U.S. presidential election.</span></p> <h3>The argument against telephone polls</h3> <p><span style="font-weight: 400;">The Brazilian association of polling institutes recently released a statement critical of telephone polls. It said such surveys don&#8217;t truly represent the Brazilian electorate, as it excludes poorer voters with less </span><a href=""><span style="font-weight: 400;">access to telephone lines</span></a><span style="font-weight: 400;">. Moreover, voters&#8217; refusal to answer telephone polls can reach 95 percent in Brazil &#8211; which could make the sample biased and dominated by more fervent voters, who would bother to answer the questions. </span></p> <p><span style="font-weight: 400;">For traditional polling institutes, the sample size of surveys conducted by Ipespe and DataPoder360 is too small to be statistically relevant. In the latest poll conducted by Ipespe, for example, 500 people were interviewed, against 2,824 face-to-face interviews by Datafolha. On the other hand, DataPoder360 interviewed 10,500 voters in May.</span></p> <p><span style="font-weight: 400;">Also, telephone polls could be limited in scope. They must be shorter, to avoid irritating responders with a laundry list of questions. Longer interviews can help map trends that a simple vote declaration might not cover. Jair Bolsonaro is ahead, sure, but could center-right candidate Geraldo Alckmin make a push and qualify for the second round? Does Ciro Gomes necessarily need Lula&#8217;s endorsement to boost his candidacy? And what about environmentalist candidate Marina Silva?</span></p> <h3>Telephone polls are still recent in Brazil</h3> <p><span style="font-weight: 400;">Despite being consolidated in European democracies and in the U.S., telephone polls are quite new to Brazil. Therefore there haven&#8217;t been enough presidential polls to analyze if this method is reliable here.</span></p> <p><span style="font-weight: 400;">However, there are some clear issues with this new method. For instance, in face-to-face interviews, respondents are given a chart which presents candidates&#8217; names in no particular order &#8211; to avoid a biased result. In phone interviews, that&#8217;s not possible, and voters listening to a long list of candidates could be influenced by the names they hear first or last.</span></p> <p><span style="font-weight: 400;">But while telephone polls can indeed offer a biased picture of how voters are behaving, they could be quite useful in a country with so few presidential polls as Brazil. If conducted regularly and with a consistent method, they can help us to understand what is going to happen in Brazil&#8217;s most unpredictable presidential race in history.

Read the full story NOW!

This article has been updated on July 4, 2018 (10:36 am, Brasília time)

Diogo Rodriguez

Rodriguez is a social scientist and journalist based in São Paulo.

Our content is protected by copyright. Want to republish The Brazilian Report? Email us at