Core CPI, month over month

Kalshi vs Polymarket: Will CPI Core rise more than 0.1% in September

Last checked 2026-09-16 10:58 UTC. Prices move constantly; the rules comparison is the durable part.

Not verified as the same bet. The venues' published terms differ in ways that could settle differently.

SETTLEMENT_POLICY_MISMATCH — both venues publish settlement policy, but the published texts diverge
REVISION_POLICY_MISMATCH — the venues publish different rules about data revisions
SETTLEMENT_GUARANTEE_UNKNOWN — the venue does not publish enough settlement policy to prove what happens in every branch (missing data, cancellation, revision)

In plain words. Where they differ: both venues publish settlement policy, but the published texts diverge; the venues publish different rules about data revisions; the venue does not publish enough settlement policy to prove what happens in every branch (missing data, cancellation, revision). Kalshi's fine print: the rules omit terms this contract family requires — the measurement basis, the revision rule, or the missing-release branch its peers publish; the rules never say what happens to open positions if the event is canceled, voided, or never takes place; the rules never say whether a later revision of the underlying number changes the outcome; the rules say what settles the contract Yes but never state what settles it No. Polymarket's fine print: the rules name more than one authoritative source, and those sources can disagree with each other; the rules never say what happens to open positions if the event is canceled, voided, or never takes place. In an ordinary outcome both contracts pay the same. The difference shows up only in the unusual case those gaps describe — a delayed release, a canceled event, a revised number — which is exactly when a paired position stops being one bet.

Venue	Contract	YES price	Taker fee at that price
Kalshi	Will CPI Core rise more than 0.1% in September? kalshi:KXCPICORE-26SEP-T0.1 Open on Kalshi	83¢	1.0¢
Polymarket US	Above 0.1% polymarket_us:cpic-uscpicore-september-mom-2026-10-14-gt0pt1pct Open on Polymarket US	99¢	0.1¢

YES price is the best ask at the last check. Fees use each venue's published taker formula at that price — see the fee calculator for any price.

Capital lock-up: about 42.5 days until the later of the two contracts settles.

Kalshi fine-print grade: F (35/100)
−20 FAMILY_POLICY_INCOMPLETE: the rules omit terms this contract family requires — the measurement basis, the revision rule, or the missing-release branch its peers publish
−20 MISSING_CANCELLATION_POLICY: the rules never say what happens to open positions if the event is canceled, voided, or never takes place
−15 MISSING_REVISION_POLICY: the rules never say whether a later revision of the underlying number changes the outcome
−10 MISSING_NEGATIVE_BRANCH: the rules say what settles the contract Yes but never state what settles it No

Polymarket fine-print grade: C (60/100)
−20 CONFLICTING_AUTHORITATIVE_SOURCE: the rules name more than one authoritative source, and those sources can disagree with each other
−20 MISSING_CANCELLATION_POLICY: the rules never say what happens to open positions if the event is canceled, voided, or never takes place

What Kalshi publishes

If the seasonally adjusted Consumer Price Index for All Urban Consumers: All Items less Food and Energy for September 2026, as published by the Bureau of Labor Statistics, increases by above 0.1%, then the market resolves to Yes. Please note that the value of the Underlying is the single-decimal value reported by the BLS. In the case of a delay in data caused by a federal government shutdown impacting the reliability of the Source Agency, the market’s latest Expiration Date will be extended to the sooner of the release of the Underlying or six months after the end of the government shutdown.

What Polymarket publishes

This market will settle to Yes if the seasonally adjusted one-month percentage change in the Consumer Price Index for All Urban Consumers excluding food and energy in September 2026 (Core CPI MoM) is above 0.1%. Outcome sourced from BLS. Settlement is based on the Consumer Price Index release published by the Bureau of Labor Statistics (BLS), currently scheduled for release on October 14, 2026. Any subsequent revisions to this figure will not be considered for settlement purposes. If the BLS does not publish Core CPI MoM for September 2026 on the Consumer Price Index scheduled release date, the first figure officially published by BLS for Core CPI MoM in September 2026 will be used for settlement. If no qualifying figure is published within three months of the scheduled release date, this market will resolve based on data from the most recent previous month with available data.