September Inflation US - Annual

The latest confirmed reading puts annual CPI inflation at 3.4% in August, which is materially above the 2.9% threshold for this market. For September to resolve Yes, the 12-month rate would need to fall by at least 0.5 percentage points in a single month, which is a meaningful move and not something that usually happens without a sharp favorable swing in the monthly CPI components. With August itself coming in at 0.4% month over month, recent price momentum was still strong enough that the burden of proof for a sub-2.9% September print is high.

There are some arguments for a decline. Core inflation has eased to 2.4% year over year, which suggests the broader disinflation process has continued under the surface, and if energy, shelter, or other volatile components soften enough in September, headline CPI can move down faster than core. However, headline inflation is being held up by a mix of sticky services and residual pipeline pressure, and the August PPI reading of 5.4% year over year points to continued upstream cost pressure rather than a clean break lower. That makes it hard to justify a very large drop in the headline annual rate without an unusually favorable September monthly report.

Market sentiment also supports a low Yes probability. The market is pricing Yes at only 2.3%, which implies participants see a sub-2.9% print as a very rare outcome. Even the nowcast mentioned in the context is still above 3%, which is directionally consistent with No. The main reason to avoid assigning an even lower probability than the market is that CPI can be volatile month to month, and a downside surprise in energy or shelter-related categories could quickly change the result. Still, absent evidence of a sharp disinflation shock, the most reasonable assessment is that inflation stays above 2.9% in September.