After each election, whatever the country, the analyzes draw maps of voter behavior and demonstrate how the sum of diverse trends in different regions composes the final result at the national level. However, in very few cases, provinces or regions are observed that, due to the composition of their population, reflect national political trends; these territories are known as bellwethers. Whether in the state of Minas Gerais in Brazil, the state of Ohio in the United States or the autonomous community of Aragon in Spain, election after election the election results are a reflection of the outcome at the national level.
According to experts Tejedor and Dader, bellwethers can be defined as cities, provinces or regions that mark or direct the national trend, although they can also be an almost exact copy of the national result. Therefore, bellwethers can also be a tool for predicting the winner of a national election.
According to experts Tufte and Sun in their book “Are There Bellwether Electoral Districts?”, bellwethers fall into two main categories. On the one hand, barometric districts predict the proportion of national votes received by the winner and, on the other hand, swingometric districts detect changes or fluctuations in the proportion of votes from one election to another. These two methods make it possible to measure the deviations in the regions in relation to the national average and, naturally, the number of times that the regions are correct a posteriori in voting for the winner of the elections.
Brazil and Minas Gerais
The recent presidential elections in Brazil reaffirmed that Minas Gerais is a very reliable bellwether state. In a previous analysis, we observed that, from 1989 to 2022, the only federal state in Brazil that fit the definitions is Minas Gerais. It was the only state, along with Amazonas, that did not fail in any of the electoral cycles for the presidency of Brazil, and its indicators are almost exactly the same as the national average of votes.
During the first round, barometric analysis showed that the vote received by Lula in Minas Gerais was only 0.14% below the national average. Furthermore, its average deviation since 1989 is 3.53 percentage points. In terms of swingometric analysis, the differences in votes from one election to another in Minas Gerais range from 3.16% to 0.80%.
This analysis allowed us to make estimates for the second round. We predicted that the result would be very close, and in the end there were 50.90% of the votes for Lula and 49.10% for Bolsonaro. The second round corresponded to our previous analysis, as observed in Minas Gerais. The percentage of votes in Minas Gerais was 0.70 points behind the national result and its variation between the first and second rounds was 0.56 points.
Spain and Aragon
In Spain, it is well known that what happens in Aragon is reflected at the national level. Our analysis from 1977 to 2019 demonstrates that the autonomous community of Aragon is the only one that consistently voted for the winner of general elections. Furthermore, if we analyze the provinces that make up Aragon, we see that in the general elections Huesca and Zaragoza always voted for the electoral winner. While the barometric analysis shows that Zaragoza is the province that best reflects the percentage of votes for the winner of the general elections.
Another interesting type of analysis we find in regional elections as predictors of what will happen at the national level. Aragón is key again. Although the general and regional elections did not coincide in the same years until 2011, we can analyze what happens a year earlier in Aragon to understand the changes at the national level.
Our analysis shows that the regional elections in Aragon are a good swingometric indicator since, since 2011, the elections have collected the same vote variations that would occur in the general elections months later. And the barometric analysis allowed us to see that the percentage of votes obtained by the most voted party in Aragon is practically identical to the percentage of votes obtained by the winner of general elections at the national level.
Bellwethers as predictors
Authors such as Edwards Tufte have explained in their research why bellwethers may be able to replicate results at the national level. One of the most widely recognized possibilities is the existence of a population that is highly representative of the national panorama. In this way, we could explain why the composition of its population reflects national political trends on a regional scale.
The sociological study of the population by strata can determine the similarities between the populations of these regions and the general population of the country according to parameters such as the proportion between men and women or the age composition of the population. Added to these similarities are others, such as the socioeconomic situation and political preferences, which lead to electoral successes election after election, whether in Ohio, Aragão or Minas Gerais.
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