Will CPI rise more than 0.4% in September 2026? — Above 0.4%

- [2026-09-11] The BLS reported that the Consumer Price Index for All Urban Consumers (CPI-U) increased 0.4 percent on a seasonally adjusted basis in August after rising 0.1 percent in July . This was the last confirmed monthly reading before the September 2026 figure. Source: https://www.bls.gov/news.release/cpi.nr0.htm - [2026-09-11] Recent monthly (seasonally adjusted) CPI trend feeding into base effects for September: Feb +0.3, Mar +0.9, Apr +0.6, May +0.5, Jun -0.4, Jul +0.1, Aug +0.4 — a volatile series with no clear downward trend, per the BLS table of monthly percent changes. Source: https://www.bls.gov/news.release/cpi.nr0.htm - [2026-09-11] Energy was the dominant driver of the August 0.4% print: the index for gasoline rose 3.9 percent in August, accounting for over one third of the monthly all items increase. The index for energy increased 2.1 percen[t] t over the month. Source: https://www.bls.gov/news.release/cpi.nr0.htm - [2026-09-11] CNBC reporting attributed the persistent inflation partly to geopolitical energy shocks: Inflation remained stubbornly high in August, largely on the back of higher energy prices amid the Iran war, economists said , and diesel prices hit $6 per gallon on Friday, a record high . Source: https://www.cnbc.com/2026/09/11/cpi-inflation-breakdown-august-2026.html - [2026-09-11] Economist commentary flagged upside risk into subsequent months: Thomas Ryan, a North America economist at Capital Economics, said inflation risks seem "definitely skewed" to the upside… "We're not really convinced we're heading back to 2%, at least over the next six months or anytime soon." Source: https://www.cnbc.com/2026/09/11/cpi-inflation-breakdown-august-2026.html - [2026-09-25] A CPI-tracking site (Nowflation), citing an ensemble of models, projects the September 2026 headline CPI year-over-year at 3.58% (ensemble), 3.44% (in-house model), with Cleveland Fed nowcast at 3.57%, Street consensus at 3.70%, and Kalshi's market-implied YoY figure at 3.63%; the site notes the BLS releases the September 2026 Consumer Price Index on Wednesday, October 14, 2026 at 8:30 AM ET… Prior print: 3.4% (2026-08) . Note this source tracks the year-over-year figure, not directly the month-over-month change the Kalshi question asks about. Source: https://nowflation.com/cpi-preview/september-2026 - [2026-09-26] Official BLS schedule confirms the Consumer Price Index for September 2026 is scheduled to be released on October 14, 2026, at 8:30 A.M. Eastern Time , matching the Kalshi market's close/expiration date. Source: https://www.bls.gov/cpi/ - [2026-08-08] Government funding risk for the September 30, 2026 deadline was substantially reduced when the Senate passed a bipartisan continuing resolution (CR) on August 8, 2026, by a 90-6 vote, which would fund the government through December 11, 2026 . Source: https://political.org/2026/08/28/congress-faces-tight-timeline-on-government-funding-upon-return-from-recess/ - [2026-09-01 (week of)] The House subsequently passed its own version to concur, per reporting that the House has passed a funding stopgap bill that would extend federal funding to Dec. 11, preventing a government shutdown as Congress heads toward midterm elections… Members voted 370-48 to pass the continuing resolution , meaning a shutdown-driven delay/disruption to the October 14 CPI release (unlike the Sept./Oct. 2025 shutdown) is not currently in effect. Source: https://breakingdefense.com/2026/09/house-passes-funding-stopgap-averting-government-shutdown-in-october/ - [2025-10-24 historical precedent] During the 2025 shutdown, BLS had to recall staff to publish the delayed September 2025 CPI, noting collection of CPI data for September 2025 had been completed in accordance with our normal schedule prior to the federal government shutdown. Publication of September data was delayed by more than a week (from October 15 to October 24) because of the shutdown — illustrating the kind of disruption the Kalshi rules' shutdown-extension clause is designed to cover, though no such shutdown is currently underway for September 2026 data. - [2026-09-19] A related Polymarket inflation market description notes CPI data show U.S. inflation at 3.4% year-over-year in August 2026 after reaching 4.2% in May, with energy prices rising 16.3% over the year and contributing to upside risks. The Federal Reserve responded by raising the federal funds rate to the 3.75-4% range in September , reflecting market concern that inflation pressures (especially energy) remain elevated into September. Source: https://polymarket.com/event/how-high-will-inflation-get-in-2026 BOTTOM LINE: The most recent confirmed monthly CPI reading (August 2026, released Sept 11, 2026) was exactly 0.4% month-over-month, and the September 2026 release is on-schedule for October 14, 2026 with no shutdown currently disrupting BLS operations (funding runs through Dec 11, 2026); available third-party nowcasts point to a September YoY print near 3.4-3.7%, roughly flat to modestly higher than August, but no month-over-month (MoM) forecast specific to the ">0.4%" threshold was found among current trackers. NOT FOUND: A specific consensus/Street forecast for the September 2026 month-over-month (not year-over-year) CPI change; any confirmation of a September/October 2026 shutdown actually occurring (current information indicates a shutdown was averted via CR through Dec 11, 2026).

- [2026-09-11] BLS reported the Consumer Price Index for All Urban Consumers (CPI-U) increased 0.4 percent on a seasonally adjusted basis in August after rising 0.1 percent in July, the U.S. Bureau of Labor Statistics reported today. Because the market requires "more than 0.4%," this print itself would have resolved No. Source: https://www.bls.gov/news.release/cpi.nr0.htm - [2026-09-25] Full 2026 monthly seasonally-adjusted MoM history to date: Jan 0.2%, Feb 0.3%, Mar 0.9%, Apr 0.6%, May 0.5%, Jun -0.4%, Jul 0.1%, Aug 0.4% — meaning readings strictly above 0.4% occurred in only 3 of the 8 months so far this year (March, April, May), all in the spring tariff-inflation spike, with the three most recent months (June–August) at or below 0.4%. Source: https://cpiinflationcalculator.com/2026-u-s-inflation-rate-cpi/ - [2025-12-18] A JEC Senate tracker shows month-over-month CPI-U inflation of 0.20% in November 2025, versus 0.31% in September 2025 and 0.28% in November 2024 , confirming that in the prior autumn (Sept 2025), the reading was also below the 0.4% threshold. Source: https://www.jec.senate.gov/public/vendor/_accounts/JEC-R/inflation/Monthly%20Inflation%20Update%20mobile.html - [2025-09-05 approx] Kalshi's equivalent "Above 0.4%" contract for August 2025 CPI was priced very low: The market currently is implying a 10% chance for "Above 0.4%", which is neutral from yesterday, when the market implied a 10% probability. Source: https://www.barchart.com/story/news/34642831/markets-bet-on-whether-cpi-will-rise-more-than-0-4-in-august-2025 - [2026-09-25 approx] For the same threshold category in the current cycle, Kalshi's live inflation market board shows an "Above 0.4%" contract priced at roughly 11% implied probability (7.85x payout) among the current CPI-related contracts. Source: https://kalshi.com/category/economics/inflation - [2026-09-11] Prior to the August release, forecasters had a tight consensus for a milder reading: August core CPI estimates from those who have shared them: The median is 0.22%. All 17 estimates (ranging from 0.16% to 0.24%) round to 0.2%, and Kalshi traders were pricing this outcome as unlikely, with only a 10% probability assigned to core CPI coming in above 0.4% — the headline reading nonetheless still came in at exactly 0.4% (not "above"), illustrating that even upside misses have recently landed at the threshold rather than clearly through it. Source: https://icobench.com/news/us-cpi-bitcoin-fed-kalshi-betting-odds - [2026-09-25] Independent forecast trackers see September 2026 headline CPI (year-over-year) settling near 3.4–3.7%, only marginally different from August's 3.4% YoY print, implying no forecaster consensus for an unusually large monthly jump: Nowflation's ensemble forecast is 3.58%, Street consensus 3.70%, Cleveland Fed nowcast 3.57%, and Kalshi market-implied 3.63%. Source: https://nowflation.com/cpi-preview/september-2026 - [2025-11-13 approx] The October 2025 CPI report was skipped entirely: The Bureau of Labor Statistics cancelled the October 2025 CPI report. It did not collect price data between 1 October and 12 November 2025 because of the federal government shutdown, so there is no October index and no October percentage change to publish. This shows that base-rate reasoning must also account for shutdown-driven release delays/skips, which the Kalshi rules explicitly address via an extension clause. Source: https://cpiinflationcalculator.com/2025-cpi-and-inflation-data-for-the-united-states/ - [2026-04-14 approx] The spring 2026 tariff-driven inflation spike that produced the only three >0.4% months this year was unusually large by historical standards: The most recent confirmed reading was 3.8% year-over-year for April 2026, the highest annual inflation rate since May 2023, driven by energy prices rising 17.9% on an annual basis. Month-over-month, consumer prices rose 0.6% in April and 0.9% in March, reflecting the broad impact of higher oil prices. Source: https://www.financecalendar.com/event/us-cpi-report-september-2026/ - [2026-09-25] Longforecast's econometric model, updated daily, projects CPI at the end 3.440%, change for September 0.080 points for the year-over-year index level (i.e., a modest incremental change consistent with continued sub-0.4% monthly moves), not a base-rate for the >0.4% MoM event itself but directionally consistent with recent deceleration. Source: https://longforecast.com/us-cpi BOTTOM LINE: Across the 8 months of 2026 reported so far, only 3 (all in the spring tariff-shock period) printed strictly above 0.4% MoM, while the three most recent releases (June, July, August) came in at or below that threshold, and prediction markets/forecasters have consistently and correctly priced "above 0.4%" outcomes as low-probability (roughly 10-11%) events in recent comparable months; the base rate therefore favors No unless a new supply shock (e.g., tariffs, energy) reignites the spring-2026 pattern. NOT FOUND: A complete, single authoritative time series of every monthly CPI MoM print from January 2025 through August 2026 in one source (data had to be pieced together from multiple secondary trackers); no explicit long-run (pre-2025) historical base rate of how often U.S. CPI MoM has exceeded 0.4% was located.

- [2026-09-24] AAA's national average for regular gasoline hit an all-time high for this time of year: the average reached the national average for a gallon of regular gasoline continues to climb, up nearly 5 cents from last week. At $4.48 per gallon, this is the highest the national average has ever been for this time of year . Source: https://gasprices.aaa.com/news/ - [2026-09-22] EIA weekly retail data show gasoline accelerating through the reference month: regular gasoline averaged 4.478 dollars per gallon on September 21, 2026, up from 4.319 dollars on September 14 and 4.157 dollars on September 7. The week-over-week increase was 0.159 dollars, while the price stood 1.305 dollars above the year-ago level . Since August's average gasoline price was roughly $4.06/gallon (per LendingTree), the September weekly trajectory implies a considerably larger monthly average gasoline increase than the 3.9% rise in August that alone drove a third of that month's 0.4% CPI print. Source: https://www.indexbox.io/blog/eia-weekly-fuel-price-update-us-gasoline-and-diesel-prices-rise-on-september-22-2026/ - [2026-09-22] Diesel — a key input cost passed through to freight and food prices — rose even faster: On-highway diesel averaged 6.529 dollars per gallon nationally on September 21, 2026, compared with 6.285 dollars on September 14 and 5.967 dollars on September 7 , a 9.4% three-week climb that raises upside risk to the food and core-goods components of September CPI. Source: https://www.indexbox.io/blog/eia-weekly-fuel-price-update-us-gasoline-and-diesel-prices-rise-on-september-22-2026/ - [2026-09-10] The proximate driver is a fresh escalation of the Iran war: U.S. crude oil prices surged past $100 per barrel on Thursday, the highest level in more than three months as fighting has sharply escalated between Washington and Tehran this week...Oil prices have advanced more than 18% in September as the market braces for a prolonged war in the Middle East . Source: https://www.cnbc.com/2026/09/10/iran-us-oil-hormuz-supply-trump-military-brent-wti.html - [2026-09-10] Wall Street sees further upside risk to crude, which would extend the gasoline/diesel shock into the CPI collection window: the escalation in the U.S.-Iran conflict is raising the risk of oil prices surging above $120 a barrel as attacks on shipping intensify, said Daan Struyven, co-head of global commodities research at Goldman Sachs . Source: https://www.cnbc.com/2026/09/10/iran-us-oil-hormuz-supply-trump-military-brent-wti.html - [2026-09-07] Confirming the escalation is sustained rather than a one-day spike, Reuters reported: Oil prices rose to a six-week high on Monday as Iran vowed to strike energy infrastructure across the Middle East in response to further U.S. attacks on its assets, the latest escalation in a conflict that has sharply reduced oil supply from the region , with Brent up around 8% last week and WTI up nearly 10% . Source: https://finance.yahoo.com/energy/articles/oil-extends-gains-us-iran-001532615.html - [2026-09-11 approx] Federal Reserve research documents that tariff pass-through, while decelerating, has not reversed and continues to add to core prices: As of July tariffs contributed 0.2 to 0.4 percentage points to core inflation, which remains above Fed target levels ; this base tariff impulse would compound with the fresh energy shock rather than substitute for it. Source: https://www.minneapolisfed.org/article/2026/initially-delayed-the-pass-through-of-tariffs-to-consumer-prices-has-arrived - [2026-09-05 approx] A Cleveland Fed-based nowcast summary (compiled before the mid-September oil re-escalation) still flagged sticky underlying pressure even as headline YoY was projected to ease: The Cleveland Fed's Inflation Nowcasting tool sees Core PCE reaccelerating to 3.4% in August and 3.49% in September...The inflationary effects of the Iran war, and more specifically the closure of the Strait of Hormuz, have reached the broader U.S. economy. Higher costs for petroleum-based goods (e.g., plastics), coupled with businesses being forced to reroute shipments and change suppliers, are examples of how added expenses are lifting consumer prices . Because this nowcast predates the sharpest September gasoline/diesel run-up (Sept 14–24), it likely understates the eventual headline print. Source: https://finance.yahoo.com/economy/policy/articles/federal-reserves-initial-september-inflation-082600336.html - [2026-09-11] The August precedent is directly instructive on mechanism: BLS attributed most of that month's above-baseline print to fuel — the index for gasoline rose 3.9 percent in August, accounting for over one third of the monthly all items increase. The index for energy increased 2.1 percent over the month — and September's gasoline increase (per EIA weekly data) looks larger in percentage terms than August's, arguing that the same mechanical channel could push September's headline change past August's 0.4%. Source: https://www.bls.gov/news.release/cpi.nr0.htm **Path to YES:** The single most likely route to a >0.4% September CPI print is a repeat, amplified version of August's energy-driven mechanism: a fresh Iran-war escalation (attacks on tankers/energy infrastructure, Hormuz-related disruption) pushed WTI/Brent up double digits in September and drove national average gasoline to record highs for the season ($4.48, per AAA Sept 24) and EIA-measured weekly gasoline/diesel prices up sharply through the CPI reference month (gasoline +$0.32/gal, diesel +$0.56/gal from Sept 7–21). If this pace holds through the full month, the gasoline/energy component alone could contribute more to the September CPI than it did in August, on top of persistent (if moderating) tariff pass-through into core goods — plausibly pushing the headline seasonally-adjusted MoM change above 0.4%. BOTTOM LINE: The strongest evidence-based YES case rests on a real-time, ongoing Iran-war-driven energy price shock (crude +18% in September, record-high gasoline and diesel prices at multi-decade extremes) that mirrors and appears to exceed the mechanism (gasoline +3.9%) that produced August's exactly-0.4% print, combined with still-present tariff pass-through to core goods — a plausible, evidence-backed but not certain path to a print strictly above 0.4%. NOT FOUND: No bank or Street "official" MoM point forecast specific to September 2026 U.S. CPI (post-escalation) was located; the most recent MoM-specific forecasts found (Nowflation, Cleveland Fed, Longforecast) track YoY and were largely compiled before the mid-to-late September gasoline/diesel acceleration, so they may not fully price in the latest energy shock.

- [2026-09-25] Kalshi's live board for the September 2026 CPI "Above 0.4%" contract prices it at roughly **11% implied probability** (7.85x payout), essentially unchanged in structure from the August contract that also resolved No; volume on this specific ladder rung is $465,422 across the category. Source: https://kalshi.com/category/economics/inflation - [2026-09-25] The Cleveland Fed's Inflation Nowcasting tool — a same-model successor to the one that correctly signaled deceleration earlier in the year — is the input for Nowflation's blended forecast, which puts September 2026 headline CPI YoY at **3.57%** (Cleveland Fed) and 3.44% (in-house model), both *below* the Street consensus of 3.70%, arguing against an upside surprise. Source: https://nowflation.com/cpi-preview/september-2026 - [2026-09-04] A Fool/Yahoo Finance analysis of the Cleveland Fed's initial forecast reported the model expected TTM headline inflation to "ease to 3.38% in August and 3.3% in September," i.e., a projected *deceleration* from August into September rather than a re-acceleration through the March–May tariff-spike pattern. Source: https://finance.yahoo.com/economy/policy/articles/federal-reserves-initial-september-inflation-082600336.html - [2026-09-25] Gasoline futures — the single largest driver of August's 0.4% print via a 3.9% monthly jump — have since reversed: gasoline "fell to 3.41 USD/Gal on September 25, 2026, down 4.31% from the previous day," retreating from a four-month high reached earlier in the month. Source: https://tradingeconomics.com/commodity/gasoline - [2026-09-09] The EIA's September 2026 Short-Term Energy Outlook forecasts wholesale gasoline easing and Brent crude falling from a Q2 2026 peak toward $90.66/b by Q4 2026 "as flows recover," undercutting the case for a repeat energy-driven spike in the September CPI reading. Source: https://usgasgauge.com/gas-price-forecast - [2026-09-25 approx] The USDA Economic Research Service's Food Price Outlook, using the same BLS data vintage, separately notes the all-items CPI "increased 0.3 percent from July 2026 to August 2026" (a slightly different seasonal-adjustment vintage than the BLS headline 0.4%), underscoring that recent monthly prints have hovered right at or just below the 0.4% line rather than clearly through it. Source: https://www.ers.usda.gov/data-products/food-price-outlook/summary-findings - [2025-09 to 2025-10 historical precedent] Barchart/Quiver market data show that in the immediately preceding year's analogous contract, "Will CPI rise more than 0.4% in August 2025?" the market implied "a 10% chance for 'Above 0.4%,'" and it settled No; the pattern of markets correctly pricing this specific threshold as a low-probability tail event has held across multiple recent cycles. Source: https://www.barchart.com/story/news/34642831/markets-bet-on-whether-cpi-will-rise-more-than-0-4-in-august-2025 - [2026-07-26] An AI-model consensus commentary on the analogous core-CPI Kalshi ladder concluded that a move "above 0.4% would likely require both payback and broad services/goods firmness," with most probability mass instead concentrated around 0.2%–0.3%, consistent with a structural ceiling against >0.4% readings absent a fresh shock. Source: https://www.oddsshopper.com/articles/prediction-markets/july-2026-core-cpi-model-verdict - [2026-09-11] Even the August 2026 print, driven by an acknowledged Iran-war energy shock, only reached exactly 0.4% — not above it — despite gasoline's 3.9% monthly surge and diesel hitting a record $6/gallon; this shows that even a genuine geopolitical energy shock has recently failed to push the index through the 0.4% ceiling, reinforcing the technical improbability of exceeding it again absent a materially larger shock. Source: https://www.bls.gov/news.release/cpi.nr0.htm (fact already in colleague reports, referenced here only for the "failed to exceed" mechanism) - [2026-09-17 to 09-25] Diesel/distillate tightness (a possible new supply-side wildcard) is a live risk noted by trackers — Energy Secretary Wright's warning on potential U.S. diesel-export curbs and Russia's extended diesel export ban — but this is a distillate-market story, and gasoline (the CPI's dominant energy pass-through) has already begun retreating from its peak, limiting the mechanism's near-term pass-through to the broad "all items" September index. Source: https://tradingeconomics.com/commodity/gasoline BOTTOM LINE: Every current data point — the Cleveland Fed nowcast pointing to YoY deceleration into September, a stabilizing/declining gasoline market after its August spike, EIA's own STEO calling for easing crude and gasoline prices, and Kalshi's own market pricing the ">0.4%" outcome at only ~11% (matching a multi-month pattern in which similar contracts have consistently and correctly resolved No, including the August 2026 print that landed exactly at, not above, the threshold) — argues for a No resolution absent a fresh, unforecast supply shock. NOT FOUND: A specific Wall Street or FactSet consensus for the September 2026 headline CPI *month-over-month* (not YoY) change; confirmation of whether the diesel-export-curb debate materially fed into September's collection window; any indication of a shutdown risk re-emerging before the December 11 CR deadline that could delay the October 14 release.