It's long been common knowledge that Brazil is a tough place to fight an away game. Over the years, stories from American fighters have trickled through, including everything from facilities that make weight-cutting harder to the raucous and antagonistic crowd in the arena. Whatever the reason, the numbers do back Brazilians in their home cage.
Since 2011, Brazilians facing non-Brazilian opponents in events held in Brazil have a record of 225-127, excluding draws and no contests. That's an impressive win percentage of 64%. Brazilians managed a winning record each year, save for 2019, when they closed the year 12-12 against foreign opponents. Their best year was 2011, when they won at an 88% clip, including a 7-1 record against non-Brazilians at UFC 134 in Rio de Janeiro.
However, matchmaking is one of the most critical factors in projecting an outcome. It's been argued that matchmakers may lean towards favorable matchups for home-cage fighters, either deliberately or unconsciously. Giving hometown heroes a squash match could make for more highlight finishes while keeping the local ticket buyers happy. Regardless of why or how, a simpler view of the home-cage advantage is that Brazilians were supposed to win more often than not because they were favored to win.
The betting markets are pretty good at predicting favorites, and Brazilian home-cage fighters average -140 betting favorites. They were supposed to win, and they did. Looking a layer deeper would be to test whether Brazilians have been performing well against these high market expectations, rather than just straight up.
Using closing odds and removing the vigorish to get a true expected win probability, we can finally answer whether or not Brazilians are exceeding market expectations for a home-cage advantage. The answer is yes. Since 2011, Brazilians have been +20 in wins above their expected win rate of 205.
But a funny thing happened in 2019. For the first time, Brazilians failed to meet market expectations by winning just 12 fights when they were expected to win 12.9 based on closing line odds. That trend continued in 2020 and 2023, when the UFC returned to Brazil for the first time since the pandemic. The betting value in backing Brazilians from 2011 to 2018 appears to have disappeared. The market has gotten wise to their advantage, or the matchmaking has improved.