Wall Street's main indexes fell on Thursday as investors awaited monetary policy clues from the Federal Reserve's annual economic symposium, while big-box retailer Walmart's quarterly results dampened sentiment.

Households earning more than $100,000 made up 75% of the company’s market share gains in the fiscal third quarter, Walmart CEO Doug McMillon said on the company’s earnings call in November.

This week's set-piece event is the Jackson Hole central-bank gathering in Wyoming, slated for Thursday through Saturday. Investors will tune into Federal Reserve Chair Jerome Powell's speech for any h