The S&P 500 snapped a three-day losing streak on Wednesday as cooling oil prices and Treasury yields boosted investor sentiment, and Polymarket traders are betting the benchmark index will build on those gains at Thursday's open. The S&P 500 rose 1.08% to close at 7,432.97 on Wednesday, while the Nasdaq Composite advanced 1.54%. The May 21 Polymarket contract implied a 66% probability that the index would open higher on Thursday. Why That Number…