S&P 500 (SPX) Up or Down on July 20?

Platform comparison

Market context

The S&P 500 closed lower on Monday, July 20, 2026, falling 0.2% to 7,443.28, which means this prediction market resolves to "Down" rather than "Up"[2][4]. This outcome contradicts the 0% crowd-implied probability for "Yes" (Up), suggesting traders correctly anticipated the decline despite earlier optimism about soft inflation data that had pushed the index to a record high of 5,847.32 just two weeks prior[1]. The divergence between the earlier record and the July 20 close highlights how quickly market sentiment can shift when defensive positioning overtakes growth optimism, a pattern seen in previous mid-year corrections where inflation expectations cooled globally but equity valuations compressed under yield pressure[1].

Traders on Polymarket should monitor upcoming Federal Reserve announcements and the weekly economic calendar, as the market is now pricing higher odds of rate cuts beginning in September following the sharp compression in Treasury yields[1]. The 10-year yield fell 12 basis points to 3.82%, expanding growth stock valuations initially, but the subsequent pullback indicates that defensive positioning ahead of the week's data releases outweighed these gains[1]. On-chain mechanics remain straightforward: USDC settles on Polygon via conditional tokens, where the resolution depends entirely on the official SPX closing price compared to the prior trading day's close, with no ambiguity around holiday schedules since July 20 was a standard trading Monday[1].

Sources: 1 · 2 · 3 · 4 · 5

Methodology

We track S&P 500 (SPX) Up or Down on July 20? across the five venues with material prediction-market liquidity. The probability shown is the live Polymarket mid; the comparison rows summarise how each venue treats the underlying contract — fees, KYC thresholds, settlement currency, deposit options. The highlighted row marks the cheapest route into Polymarket's order book.

Resolution & payout

Settlement runs on-chain. Polymarket's contract logic separates YES and NO shares as conditional tokens; at resolution the winning share lifts to $1.00 and the losing one to $0. The outcome input comes from the UMA Optimistic Oracle, which secures against bad resolution with a bond + dispute window.

Once finalised, the smart contract pays USDC to the holders' wallets within minutes — no withdrawal fees beyond Polygon network gas. Kalshi settles in USD via CFTC clearance, Betfair in account currency net of commission, Manifold in play-money mana with no cash-out.

FAQ

Is this market available outside the US?

Polymarket itself is geo-blocked in the US/UK/EU. Always check the legal status of prediction markets in your jurisdiction before trading.

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.

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.