US Consumer Inflation Accelerates to 3.7% in September, Driven by Fuel Prices

What happened

The US Consumer Price Index (CPI) accelerated in September, advancing 0.6% for the month, marking the largest increase in five months. On an annual basis, the CPI rose to 3.7%. One of the main factors behind this inflationary pressure was the surge in fuel prices, with gasoline recording a 34% increase compared to September 2025, partly due to the war in the Middle East.

Why it matters

The persistence of high inflation levels is a significant challenge for the economy and monetary authorities. The acceleration of the CPI in September, especially driven by volatile components like fuel, signals that inflationary pressures are still present. For the Federal Reserve (Fed), controlling inflation is a priority, and data like this increases the likelihood that the institution may be led to adopt more restrictive measures. Furthermore, inflation is a central theme in the American political landscape, posing one of the main challenges for the Republican Party's campaign in the upcoming November elections, which will determine control of the House and Senate.

Market impact

• Interest rates and bonds: Higher inflation news tends to push US Treasury yields upward. Following the CPI release, the two-year Treasury yield rose from 4.797% to 4.808%. This reflects expectations that the Fed may raise interest rates again, making existing debt securities less attractive and demanding higher yields for new bonds.
• Dollar and exchange rates: A scenario of higher inflation in the US, potentially leading to additional monetary tightening by the Fed, tends to strengthen the dollar. Higher US interest rates attract foreign capital seeking greater returns, appreciating the American currency against other currencies. For the Brazilian real, this could mean downward pressure.
• Equities: Stock markets generally react negatively to expectations of higher interest rates. Elevated interest rates increase the cost of capital for companies, reduce the attractiveness of equity investments compared to fixed-income assets, and can slow economic growth. The S&P 500 declined 1.1%, and the Nasdaq, more sensitive to interest rates, fell 1.88% after the data release.
• Commodities: Rising fuel prices were a key factor in September's inflation. While the news itself does not directly alter future commodity prices, it highlights inflation's sensitivity to supply shocks, such as the war in the Middle East, which impact oil and, consequently, gasoline prices.
• Brazil: The prospect of higher interest rates in the US tends to have a negative impact on Brazil. Rising Treasury yields make Brazilian assets relatively less attractive, potentially leading to capital outflows and pressuring the exchange rate (stronger dollar against the real). Furthermore, a global environment of higher interest rates can complicate domestic monetary policy, especially if the Brazilian Central Bank is in an easing cycle.

What to watch

Investors should closely monitor upcoming Federal Reserve communications and decisions, especially this month's meeting, where another rate hike may be considered. Additionally, upcoming inflation data (such as CPI and PCE), payroll reports, and other economic activity indicators will be crucial for assessing the trajectory of US monetary policy and the sustainability of inflationary pressures.

Scenarios

Base Case: The Fed maintains a vigilant stance, and elevated inflation may lead to another interest rate hike in the short term, keeping Treasury yields high and the dollar strong. Equity markets may remain volatile. Risk Scenario: Inflation proves more persistent than expected, requiring a more aggressive monetary tightening cycle by the Fed, which could lead to a more pronounced economic slowdown and increased risk aversion in global markets.

Original source: Valor Econômico. For information only, not investment advice.