Scan: GDP growth in 2028? — 1.6% to 2.0%

date	predicted	market price	confidence
2026-08-29	10%	9%	62%
2026-08-22	12%	12%	62%
2026-06-13	12%	10%	50%

1. Planner Fable 5.1 · Fermi decomposition + tool plan

Tools chosen: kalshi_direct kalshi_related polymarket_related fred article_search claude_news code_execution

Sub-questions (Fermi decomposition)

What are the current Kalshi prices across all KXGDPYEAR-28 brackets, and what implied distribution do they yield for 2028 growth?
What is the current consensus/long-run forecast for US real GDP growth in 2028 (Fed SEP longer-run, CBO 10-year outlook, Blue Chip, SPF)?
Historically, how often has annual US real GDP growth landed within a given 0.4pp bin centered near trend (~1.8%) roughly 2-3 years ahead of forecast — i.e., what is the base rate given forecast error dispersion?
Does Kalshi resolve on annual-average (year-over-year) GDP growth or Q4/Q4 growth, and which BEA release (advance estimate in Jan 2029) is used?
What is the estimated US potential/trend GDP growth for 2027-2028 given labor force/immigration and productivity (AI) assumptions?
What is the probability of a US recession occurring in 2027-2028, which would push growth well below the 1.6-2.0% bin?
What do the KXGDPYEAR-26 and -27 bracket markets imply about near-term growth momentum heading into 2028?

Planner reasoning

This is a long-horizon question about US real GDP growth in 2028 landing in the 1.6%-2.0% bin. Key inputs are the Kalshi bracket prices (implied distribution across bins), consensus long-run forecasts (Fed SEP longer-run, CBO, Blue Chip, Survey of Professional Forecasters) for 2028, the historical dispersion of annual GDP growth relative to trend (base rate of landing in a 0.4pp-wide bin), and the exact resolution convention (annual-average vs Q4/Q4). Recession probability over the horizon and current trend/potential growth estimates also matter.

2. Research Parallel tool calls

tool	status	time	items	summary
kalshi_direct	OK	0.2s	1	## This Market's Kalshi Data 1.6% to 2.0% (KXGDPYEAR-28-B1.8) - Current price (probability): 11.00% - 7-day price change: +0.00% - 30-day price change: -1.00% - Average daily volume: 675 contracts - Price range: 5.00% - 12.00% - Data points: 16 days
kalshi_related	OK	4.0s	2	2 related markets / summaries. series KXGDPYEAR: 0 markets (skipped 100 no-signal) \| keyword 'GDP growth 2028': ok \| keyword 'GDP growth 2027': ok \| keyword 'recession': no matches
polymarket_related	OK	3.9s	0	Scanned 100 active Polymarket markets, kept 0 matches. keyword 'GDP 2028': 0 markets \| keyword 'GDP growth': 0 markets \| keyword 'recession 2027': 0 markets \| keyword 'recession 2028': 0 markets
fred	OK	5.7s	6	Fetched 6 FRED series (lookback=1095d) (via search 'real GDP growth annual').
article_search	OK	4.2s	28	Fetched 28 unique articles across 4 queries (lookback=90d). 'US GDP growth forecast 2028': 10 articles \| 'CBO economic outlook long-term GDP growth': 10 articles \| 'Fed longer-run GDP growth projection': 10 articles \| 'recession probability 2027 2028 economists': 10 articles
claude_news	OK	34.2s	11	Fed SEP (Summary of Economic Projections) - June 2026 SEP: median real GDP growth (Q4/Q4) projected at 2.2% for 2026, 2.3% for 2027, and 2.2% for 2028 (up from 2.1% in the March projection) . https://www.tradingkey.com/analysis/economic/central-banks/261973912-fed-federal-fomc-2-economic-projec
code_execution	OK	32.0s	0	Historical base rate (1985–2024, n=40): - Exactly 5 years fell within [1.6, 2.0]: 1990 (1.9), 2002 (1.7), 2007 (2.0), 2011 (1.6), 2016 (1.8) → base rate = 5/40 = 12.5% - Full-sample mean = 2.67%, sd = 1.69 (reflects volatile pre-2010 decades; more recent/trend growth is lower and less volati

3. Evidence Brief Sonnet 5 · 6292 chars

# Event Kalshi market KXGDPYEAR-28-B1.8: resolves YES if US real GDP growth in 2028 falls between 1.6% and 2.0% (inclusive-ish bucket), based on BEA data. # Outcomes to forecast - Yes (2028 real GDP growth in [1.6%, 2.0%]) - No (growth outside that band) # Kalshi market anchor **Current YES price: 11%** (down from 12% high, up from 5% low over past 16 days; 30-day change -1%; 7-day flat). Average daily volume ~675 contracts — modest but tradeable liquidity. This is the consensus to beat. # Sub-question answers 1. **Bracket prices/implied distribution** — Only two brackets directly retrieved: KXGDPYEAR-28-B1.8 (1.6-2.0%) at 11%, and KXGDPYEAR-36-B2.8 (2.6-3.0%, different year) at 9%. Full 2028 bracket ladder not fully surfaced; nominal GDP growth 2028 "Above 3.0%" market prices at 66%. [kalshi_direct/related] 2. **Consensus long-run forecast** — Fed June 2026 SEP median real GDP growth 2028 ≈2.2% (Q4/Q4), longer-run potential ~2.0%; Dec 2025 SEP central tendency 1.8-2.1% (midpoint 1.9%). CBO (Dec 2025/Jan 2026) projects 2027-2028 average real GDP growth of ~1.8%/year. [claude_news, Fed SEP, CBO] 3. **Historical base rate** — Over 1985-2024, only 5/40 years (12.5%) landed within a 1.6-2.0% band. Mixture/normal models incorporating recession risk and forecast-error dispersion converge on ~12-16%, central estimate ~13-14%. [code_execution] 4. **Resolution basis (annual-avg vs Q4/Q4)** — Not explicitly confirmed in Kalshi rules; BEA reports both full-year average and Q4/Q4 rates, and Kalshi's methodology wasn't found in search. Ambiguity noted as a real uncertainty. [claude_news] 5. **Potential/trend growth 2027-2028** — Fed longer-run potential ~2.0%; CBO ~1.8% average, driven by reconciliation-act-boosted investment/labor supply offset by tariffs and reduced immigration-driven labor force growth. No explicit AI-productivity uplift incorporated in official estimates. [CBO, claude_news] 6. **Recession probability 2027-2028** — No explicit numeric probability found in article search; qualitative concern present (CBO baseline "assumes no recessions"; WaPo opinion piece flags recession risk to debt outlook). Modeling assumed p(recession)≈25-35% as a scenario input, not a sourced consensus figure. [WaPo, code_execution assumption] 7. **KXGDPYEAR-26/-27 momentum implications** — KXGDPYEAR-27 "0.0% or Below" bucket priced at only 6% (down 4pts in 7 days), implying market sees outright 2027 contraction as unlikely. No full 2026/2027 mid-range bracket data retrieved to infer momentum precisely. [kalshi_related] # Key facts (high-confidence, factual) 1. [kalshi_direct] Current YES price for this exact bucket = 11%, range 5-12% over 16 days. 2. [Fed SEP Dec 2025] 2028 median real GDP growth forecast (Q4/Q4) = 1.9%, central tendency 1.8-2.1%; longer-run potential = 2.0%. 3. [Fed SEP June 2026] 2028 median raised to 2.2% (Q4/Q4). 4. [CBO, Jan 2026] 2027-2028 average real GDP growth (Q4/Q4) projected at 1.8%. 5. [BEA/CNN/BBC] Q2 2026 actual GDP growth came in at 1.5% annualized, below the 2.1% Q1 rate and below consensus (2.1% expected) — signals recent deceleration. 6. [FRED A191RL1Q225SBEA] Quarterly growth has been volatile: -0.6% (Q1'25) to 4.4% (Q3'25) to 1.5% (Q2'26), reflecting high noise. 7. [code_execution] Historical base rate for a year landing in a 0.4pp band near trend ≈12.5% (5/40 years, 1985-2024). # Cross-market signals - Kalshi related: KXGDPYEAR-27 "0.0% or Below" priced at just 6%, suggesting market assigns low recession-level-contraction odds for 2027. Nominal GDP growth 2028 "Above 3.0%" priced at 66%, consistent with real growth + inflation near/above 2% real growth zone but not decisive for the exact real bucket. - Polymarket: No matching GDP markets found. - Sportsbook implied: N/A (not applicable to economic data market). # Analyst opinions and speculation - CNBC/WaPo coverage highlights AI infrastructure investment as a growth driver but also a widening trade deficit drag; consumer spending resilient but outlook sentiment souring (CNBC survey: 41% expect economy to worsen vs 29% better). - Fed dot plot trending toward slightly higher 2028 growth estimates (1.9%→2.2%) between Dec 2025 and June 2026 SEPs — a modest upward drift outside the 1.6-2.0% Kalshi band. - CBO's 1.8% central estimate sits squarely inside the bucket, while Fed's more recent 2.1-2.2% median sits just above it — highlighting genuine forecaster disagreement straddling the bucket edge. # Directional lean per outcome - **Yes (1.6-2.0%)**: Supported by CBO's 1.8% point estimate landing inside band; Fed's Dec 2025 central tendency (1.8-2.1%) substantially overlapping. Opposed by: Fed's more recent June 2026 SEP drifting to 2.2% (above band); historical base rate of only ~12-16% for any single 0.4pp bucket; high quarterly growth volatility makes precise annual landing in a narrow band inherently low-probability. - **No (outside 1.6-2.0%)**: Supported by base-rate/dispersion models (~85-88% probability outcome falls outside this specific band, split between higher-growth and recession/low-growth scenarios); Fed's upward-trending projections pointing above 2.0%; quarterly growth volatility (0.5%-4.4% swings) increasing tail risk in both directions. # Gaps / unknowns - Full Kalshi bracket ladder for 2028 not retrieved — cannot compute complete implied distribution or check for arbitrage/consistency across buckets. - Kalshi's exact resolution methodology (annual-average vs Q4/Q4, which BEA vintage) unconfirmed — could shift outcome interpretation given Fed variance between the two conventions (SEP Q4/Q4 2.2% vs. plausible annual-average closer to CBO's 1.8%). - No sourced quantitative 2027-2028 recession probability estimate. - No Polymarket cross-check available. # Calibration anchors - Kalshi current YES price: **11%** (primary anchor). - Historical base rate for a similar 0.4pp band centered near trend: ~12.5% (1985-2024). - Model-based synthesis (mixture/normal, incorporating recession risk & forecast error): **~12-16%**, central ~13-14%. - These converge closely with the Kalshi price (11%), suggesting the market is reasonably well-calibrated, perhaps very slightly underpriced relative to base-rate/model midpoint (~13-14% vs 11%), but within noise given liquidity and bracket-boundary ambiguity.

4. Forecasters Fable 5.1 + GPT-5.6 Sol · in parallel

claude-fable-5-1

58% conf

Yes	13%
No	87%

The Kalshi anchor for the 1.6-2.0% bucket is 11%, and independent checks converge on a similar figure: the 1985-2024 base rate for landing in any given 0.4pp band near trend is ~12.5%, and mixture models with recession risk yield ~12-16%. Consensus point forecasts straddle the band (CBO 1.8% inside; Fed June 2026 SEP 2.2% just above), so the bucket sits near the mode of the forecast distribution, but a 2.5-year-ahead forecast error SD of ~1.5pp implies only ~11-14% mass in a 0.4pp window. Recent deceleration (Q2 2026 at 1.5%) and Fed's upward drift roughly cancel directionally. Unresolved annual-average vs Q4/Q4 methodology adds noise but does not shift the central estimate much, so I land slightly above the market at 13%.

gpt-5.6-sol

68% conf

Yes	13%
No	87%

The 11% Kalshi YES price is the primary anchor and aligns closely with the 12.5% historical frequency for a similarly narrow growth band. CBO's 1.8% forecast supports YES, but the newer Fed median of 2.2% points just above the bucket, while forecast dispersion and recession risk make an exact 0.4-point landing unlikely. Mixture models placing YES around 12-16% justify a modest increase from the market price to 13%, though uncertainty about the resolution methodology limits conviction.

5. Devil's Advocate Sonnet 5 · red-team critique

Both forecasters converge on nearly identical 13% estimates using the same evidence, but neither meaningfully engages with the resolution-methodology ambiguity (annual-avg vs Q4/Q4) as a bimodal risk — if Q4/Q4 is used, Fed's 2.2% median falls clearly outside the band, whereas CBO's annual-average 1.8% falls inside, meaning the true probability could be quite different depending on which convention Kalshi uses, yet both treat this as a minor noise adjustment rather than a structural uncertainty that could shift the estimate several points in either direction.

Neither forecast explores the incomplete bracket ladder gap — the brief notes "Full 2028 bracket ladder not fully surfaced" and flags a nominal GDP "Above 3.0%" market at 66%, which could have been used to cross-check consistency (e.g., implied inflation + real growth combinations) but neither analyst attempted this triangulation to sanity-check the 11-13% figure.

Both forecasters give a "modest increase" to 13% from the 11% market price with weak justification for why the market is underpriced rather than simply noisy; given only ~675 avg daily volume and a bid-ask-like drift from 5% to 12% over 16 days, the case for a specific 2pp edge over the anchor is not strongly argued — this could just as easily be reversed given liquidity-driven noise.

Neither forecast weighs the recent momentum data (Q2 2026 actual at 1.5%, below consensus, following volatile swings from -0.6% to 4.4%) as a signal that could shift 2028 base-year comparisons or forecaster revisions — this deceleration signal is mentioned but dismissed as "roughly canceling" Fed's upward drift without any quantitative treatment of how a lower 2026/2027 base could mechanically affect 2028 YoY growth optics.

Both forecasts ignore the cross-market signal from KXGDPYEAR-27 "0.0% or Below" priced at 6%, which implies the market sees low recession risk for 2027 — neither integrates this into their own recession-probability assumption (the brief's code_execution used an unsourced 25-35% recession prior) to check whether their mixture-model inputs are consistent with actual market-implied recession odds.

Confidence levels (0.58 vs 0.68) diverge notably despite identical point probabilities and nearly identical reasoning — this inconsistency in stated confidence is unexplained and neither rationale justifies why one analyst should be meaningfully more confident than the other given they cite the same evidence base.

6. Aggregator Fable 5.1 · final calibrated forecast

12% (63% confidence)

Yes: 12% No: 88%

Both forecasters and the market converge tightly (11-13%), and the independent checks—12.5% historical frequency for a 0.4pp band near trend, and mixture models at ~12-16%—support that range. The critique correctly notes the resolution-methodology ambiguity is structural: under Q4/Q4 the Fed's 2.2% median sits above the band, while under annual-average the CBO's 1.8% sits inside, but both cases still leave a 2.5-year-ahead forecast error SD of ~1.5pp, which caps mass in any 0.4pp window at roughly 10-15% regardless. The critique's point that a 2pp edge over a thinly traded market is weakly justified is also fair, so I shade slightly back toward the anchor. Final call: 12% Yes, 88% No.

Pipeline Timing

Total pipeline time: 128.4s

Per-tool research timings shown in the Research section above.