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S&P 500 (SPX) Up or Down on May 21?

How the prediction-market book is pricing "S&P 500 (SPX) Up or Down on May 21?" right now, with a side-by-side platform comparison and zero-fee CTAs.

100% YES 0% NO Volume: $171K Closes: 21 May 2026
Trade on PolyGram →

Platform comparison

PlatformYES oddsNO oddsFeeKYCSettlement
PolyGram Pick
polygram.ink
100% 0% 0% (USDC on-chain) No-KYC up to $1,500 USDC, auto via UMA oracle Open on PolyGram →
Polymarket
polymarket.com
100% 0% 0% Geo-blocked in US/UK/EU USDC, on-chain Open on PolyGram →
Kalshi
kalshi.com
Up to 7% per trade US-only, KYC required USD Open on PolyGram →
Betfair Exchange
betfair.com
2-5% commission Full KYC from first trade GBP / EUR Open on PolyGram →
Manifold Markets
manifold.markets
Play-money (mana) None — play-money Mana (no cash-out) Open on PolyGram →

Live odds for Polymarket-based markets come from the Polygon order book. Non-Polymarket venues show attributes only; clicking any row opens the market on PolyGram.

Market context

The S&P 500 finished the previous session at 7,432.97, leaving today’s move dependent on whether the index can extend a run that has taken it to fresh highs this month. That backdrop matters because the market is already pricing in an “Up” outcome at 100%, so the decision point is not direction in the abstract but the size and durability of any late-session move before the 20:00 UTC settlement cut-off.

Recent comparable episodes suggest that an index already near record territory can still finish either side of the prior close on a thin catalyst, especially after a strong multi-day rally. Goldman Sachs has recently argued the S&P 500 could end 2026 at 7,600, while FRED’s latest reading shows the index well above 7,400, underscoring how much of the year’s gain has already been pulled forward. In that context, a flat or slightly lower close would be more about intraday profit-taking than a change in the broader trend.

For today’s tape, traders will be watching Treasury yields, any late-day macro releases, and whether the post-open tone from earnings and Fed commentary holds into the close. The main near-term dependency is whether yesterday’s strength in large-cap technology and broader risk appetite continues without a fresh headline shock; if not, a modest pullback would be enough to flip an “Up” market into “Down” for settlement purposes.

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page is a comparison snapshot: one live quote (Polymarket), four reference venues with their key attributes, and a single execution path — every trade button routes to PolyGram, which mirrors the Polymarket order book directly.

Resolution & payout

At resolution the UMA oracle takes over: a proposer posts the outcome with a bond, any token holder can dispute within two hours. Without dispute the result is accepted and the smart contract distributes USDC instantly.

On Kalshi (CFTC-regulated) resolution runs through their in-house clearing engine in USD. Betfair Exchange settles after match end in the account's local currency. Manifold pays no cash — only its in-platform "mana" currency.

FAQ

Is this market available outside the US?
PolyGram is available in most jurisdictions where Polymarket isn't directly accessible. Polymarket itself is geo-blocked in the US/UK/EU. Always check local regulations.
How does resolution work?
Through the UMA Optimistic Oracle on Polygon: a proposer submits the outcome, a two-hour challenge window opens, and USDC payouts settle automatically once the result is final.
What's the difference between YES and NO shares?
A YES share pays $1.00 if the event happens, $0 otherwise. A NO share pays $1.00 if the event doesn't happen. The market price between 0¢ and 100¢ is the implied probability.
How fast are USDC deposits?
Polygon credits deposits after 12 confirmations — usually under 30 seconds. Withdrawals follow the same path and land back in your wallet within minutes.
Do I need to KYC for this market?
Not under $1,500 of lifetime trading volume. Above that threshold, PolyGram triggers a quick verification flow that finishes in minutes.

Trade S&P 500 (SPX) Up or Down on May 21? on PolyGram

Live order book, 0% fees, USDC settlement in seconds.

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