TOTAL VOLUME:
$66b
24H VOL:
$398,877,831
24H TRANSACTIONS:
647,445,881
OPEN INTEREST:
$1,477,629,845
622,934
Markets across
14,083
events
MATCHED EVENTS:
1,257
PLATFORM COVERAGE:
4
Polymarket:
49%
VS.
Kalshi:
51%
What will S&P 500 (SPX) close at end of 2026?
Will S&P 500 (SPX) close at >$8,000 in December?
$
$20
$50
$100
$500
Description
These markets ask where the S&P 500 will close on the final trading day of December 2026. Kalshi offers granular 200-point brackets across the full range, while Polymarket segments the market into five broader price bands ($6,000-$7,000, $7,000-$7,500, $7,500-$8,000, >$8,000, and <$6,000). Both use the official closing price on December 31, 2026 at 4pm EST as the settlement value.
PredictionHero - Resolution Divergence Alerts (RDA)
Divergence Detected
Issue:
Kalshi defines 27 overlapping YES-resolution brackets covering the entire possible SPX range (below 4000 to above 9000), making the market logically unresolvable as a binary contract. Polymarket defines 5 mutually exclusive price ranges with exactly one resolving YES, providing a standard price-bracket settlement structure.Hero Tip:
Kalshi's market is fundamentally broken—every possible SPX close triggers YES across multiple overlapping conditions, violating binary market logic. Do not trade Kalshi. Polymarket's structure is standard: pick the bracket you believe SPX will close in; exactly one resolves YES. Trade Polymarket only.Critical Divergence Points:
Kalshi:
27 conditions, all resolving to YES. Conditions 1–27 partition SPX into 200-point brackets from below 4000 to above 9000. Every possible closing price satisfies at least one condition. Example: SPX = 7500 triggers YES on conditions 10 (7400–7599.99), 9 (7600–7799.99 is false), and multiple others. The market cannot distinguish between outcomes.Polymarket:
5 mutually exclusive brackets: <6000, 6000–6500, 6500–7000, 7000–7500, 7500–8000, >8000. Exactly one resolves YES based on official Yahoo Finance closing price on final trading day of December 2026. Tie-breaking rule: if price falls exactly on bracket boundary, resolves to higher bracket.
Polymarket
This market will resolve according to the official closing price for S&P 500 (SPX) on the final trading day of December 2026. If the reported value falls exactly between two brackets, then this market will resolve to the higher range bracket. If the final trading day of the month is shortened (for example, due to a market-holiday schedule), the official closing price published for that shortened session will still be used for resolution. If no official closing price is published for that session (for example, due to a trading halt into the close, system issue, delisting, or other disruption), the market will use the last valid on-exchange trade price of the regular session as the effective closing price. The resolution source for this market is Yahoo Finance, specifically the S&P 500 (SPX) "Close" prices available at https://finance.yahoo.com/quote/%5EGSPC/history, published under "Historical Prices."
Kalshi
The S&P 500 index value on December 31, 2026 at 4pm EST determines which outcome resolves to Yes. The measurement is taken from the official closing price at that specific time and date. Resolution occurs at the sooner of the first release of the data or one week after December 31, 2026. Per Kalshi Rulebook modifications for indices markets, the Source Agency and Underlying for this index have been modified—see the rules for additional information on data sourcing and calculation methodology.
Frequently asked questions
Prediction market odds reflect real-money consensus from thousands of traders betting on SPX year-end 2026 levels, whereas analyst forecasts are typically point estimates or ranges from equity strategists. Markets embed forward-looking expectations about GDP growth, inflation, Fed policy, and corporate earnings through 2026, while analyst views often lag market repricing. The prediction market approach captures tail risks and probability distributions that single-point forecasts miss, making them complementary tools for understanding the full spectrum of potential outcomes rather than competing predictions.
Kalshi and Polymarket can show different implied probabilities for the same outcome because of liquidity, fee structure, participant mix, and how each venue defines the contract. Kalshi and Polymarket serve different trader bases, use distinct contract structures, and operate under separate regulatory frameworks. Kalshi shows 3.0% for SPX below 4000, while Polymarket reflects 11.5% for SPX below 6000—different strike levels create incomparable odds. Liquidity concentration, arbitrage friction, and timing of order flow also drive spreads. Traders exploit these gaps by comparing outcomes across venues, so persistent divergence signals either genuine disagreement on tail probabilities or temporary imbalances awaiting correction.
Major catalysts include Federal Reserve policy shifts, inflation and employment data, geopolitical escalation, corporate earnings revisions, and changes to fiscal or trade policy. Recession or expansion cycles over the next two years will heavily influence equity valuations. Sector rotation driven by AI adoption, energy transitions, or rate-sensitive industries can reshape index composition. Unexpected shocks—financial crises, regulatory changes, or earnings surprises—create sharp repricing. Traders monitor economic calendars, Fed communications, earnings seasons, and macro surveys to anticipate moves in SPX year-end 2026 odds.
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