Platform comparison
| Platform | YES odds | NO odds | Fee | KYC | Settlement | |
|---|---|---|---|---|---|---|
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
This market will resolve to "Up" if the official S&P 500 Index closing price for S&P 500 (SPX) on Thursday, May 21, 2026 is higher than the official S&P 500 Index closing price for SPX on the most recent prior trading day. This market will resolve to "Down" if the official S&P 500 Index closing price for S&P 500 (SPX) on Thursday, May 21, 2026 is lower than the official S&P 500 Index closing price for SPX on the most recent prior trading day. E.g., ordinarily, a market on Monday would refer to
Methodology
This page reviews S&P 500 (SPX) Up or Down on May 21? across five venues. We show live odds for Polymarket-based markets (sourced from the Polygon order book); for other venues we list platform attributes, since the comparable contracts are not exposed via a public API on every venue. Every CTA points at PolyGram — the application we operate, where you trade directly against the Polymarket order book at 0% fees.
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.
- 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.
- How reliable are the quoted odds?
- The YES/NO percentages are the live mid-prices of the Polymarket order book. On deep markets they move every few seconds; on thinner ones you'll see short plateaus.
Trade S&P 500 (SPX) Up or Down on May 21? on PolyGram
Live order book, 0% fees, USDC settlement in seconds.
Trade on PolyGram →