Tyler Jacobsma is the founder of Flowframe.xyz, which provides in-depth content and tools for prediction market traders.
April CPI on Polymarket
The trade: YES on 3.5% at 14¢. The Cleveland Fed's nowcast says April CPI will land at 3.56% year-over-year, almost exactly on the line between the 3.5% and 3.6% buckets. Polymarket prices 3.6% at 31¢ and 3.5% at 14¢, that’s only a 1 one basis point difference, but a very different contract price. I think that’s too big a discrepancy.
Companion hedge: NO on 3.8% at ~81 cents, a high-probability low-payout fade.
How the Buckets Actually Work
Polymarket's market resolves on the rounded year-over-year change in headline CPI. Every bucket covers a 0.1-point band. 3.5% wins if the unrounded reading lands anywhere from 3.45% up to 3.55%. 3.6% wins from 3.55% to 3.65% and so on.
So the whole trade comes down to where one number lands inside a 0.1pp window. The Cleveland Fed's nowcast, released today, April 24 (about three weeks before the May 12 release), sits at 3.56%. One basis point above the 3.55% boundary. The nowcast's typical accuracy this close to the release date is 8 to 15 basis points up or down, so the true distribution buckets should have similar contract price, not lopsided 3-to-1 in one direction like we are currently seeing.
Here is what each bucket needs from April's monthly index move (BLS NSA, the unseasonally-adjusted series the headline rounds from):
| YoY Bucket | Monthly NSA Change Needed | Polymarket YES Price |
|---|---|---|
| 3.4% | +0.40% to +0.49% | 5.4¢ |
| 3.5% | +0.50% to +0.59% | 14.0¢ |
| 3.6% | +0.60% to +0.69% | 31.0¢ |
| 3.7% | +0.70% to +0.79% | 28.7¢ |
| 3.8% | +0.80% to +0.89% | 19.4¢ |
| 3.9% | +0.90% to +0.99% | 4.2¢ |
For context: the 10-year average April monthly change (ex-COVID) is +0.45%. The 5-year 2021–2025 average is +0.52%. A normal-seasonal April lands somewhere in the 3.4–3.5% range.
What the Data Actually Says About April
The big swing factor is gasoline. Retail regular averaged ~$4.10 in April, month-to-date versus $3.64 in March, a 12.6% jump. April has a positive seasonal kicker from the summer-blend switchover, so the seasonally-adjusted contribution is closer to +7% to +10%. That adds roughly 25 to 35 basis points to the headline monthly print. This is also why we are unlikely to see a
repeat of March’s big +0.9% jump. Gas prices are higher, but it's more about the rate of change, which is slower.
Core inflation looks mixed. Used cars should be positive again. Airfares are a clear risk to the upside as jet fuel roughly doubled in late February through early March, and CPI airfares were already running +14.9% YoY in March. However, shelter remains the disinflationary anchor, with Zillow rent growth still slowing. Tariffs continue to pass through, with the Yale Budget Lab pegging the average effective rate at 11.0% after the April 2 executive order.
Adding it up: April monthly NSA likely lands between +0.55% and +0.65%, with a center near 3.60% YoY and a standard deviation around 12 basis points.
EY-Parthenon calls for ~3.6%. JPMorgan Asset Management's revised projection implies 3.4–3.5%. Goldman's $115/barrel oil-shock case implies 3.7–3.8%, but Brent has averaged ~$98 in April, well below that.
Where the Market is Wrong
Run a normal distribution with mean 3.60% and SD 0.12. Here is how the model probabilities compare to what Polymarket is pricing:
| Bucket | Model Probability | Market | Gap |
|---|---|---|---|
| 3.5% | 25% | 14% | +11pp underpriced |
| 3.6 | 31% | 31% | flat |
| 3.7% | 20% | 29% | -9pp overpriced |
| 3.8% | 7% | 19% | -12pp overpriced |
As you can see, not really close to 14%. The market looks focused on the nowcast number itself rather than the boundary it sits next to.
The 2 Trades
Trade 1 — YES on 3.5% at 14¢. Best risk-adjusted edge. Wins if April's monthly NSA change lands between +0.50% and +0.60%, which is exactly where the Cleveland Fed nowcast points after seasonal adjustment.
Trade 2 — NO on 3.8% at ~81¢. +15% expected ROI at a ~93% hit rate. The 3.8% bucket essentially requires a repeat of March's gasoline-driven surge, which looks unlikely with crude already off its peak.
Risks
Three scenarios that ruin YES on 3.5%:
- Gasoline stays hot through the rest of April. A monthly average above $4.15 (vs March's $3.64) pushes monthly NSA toward +0.75% and YoY into the 3.65–3.70% range. The April 20 EIA reading of $4.044 is moving in the wrong direction for this scenario, but the Hormuz situation continues to be volatile and not fully resolved.
- Shelter catch-up is bigger than expected. Goldman and JPM both flag an extra month of shelter inflation in April. Shelter printing +0.5% MoM instead of the expected +0.3% adds about 7 basis points to the headline number and risk pushing it to the higher bucket.
- Airfare accelerates. If carriers raise fares aggressively rather than just adding fuel surcharges, the core services inflation jumps. Airfares already at +14.9% YoY in March are showing this is a real risk.
- Scenarios that strengthen the 3.5% thesis are at least as plausible: crude kept softening after the April 7 ceasefire, natural gas hit a multi-year low, the dollar weakened only modestly, and wage growth slowed to its lowest since May 2021.
Bottom Line
The market is pricing 3.56% as if it sits comfortably inside the 3.6% bucket. It sits one basis point from the 3.5% line. Given how tight the Cleveland Fed nowcast historically is this close to release, the true probability of landing on either side of that boundary should be closer to even odds, not a 31/11 split.
YES on 3.5% at 14¢ is the trade. NO on 3.8% at ~81¢ is the hedge.
