Amazon Shares Tumble 3.04% on Record $15.76B Volume as Third-Busiest Trade Day

On September 23, 2025, , ranking third in market activity for the day. The decline followed mixed signals from recent operational updates and evolving market dynamics.

Analysts noted that the stock's volatility was partly driven by investor reassessments of its long-term growth trajectory amid shifting e-commerce demand patterns. While third-party seller policies remain a focal point, recent regulatory scrutiny has introduced uncertainty about potential margin pressures. This contrasts with earlier optimism tied to AWS expansion and AI integration plans.

Market participants also observed that the broader tech sector's rotation into value stocks may have impacted Amazon's relative performance. However, the stock's liquidity profile remains robust, . .

To run this back-test properly we need a few extra details and (because of tool limitations) we may have to agree on a practical way to proxy the "top-500-by-volume" basket. Key points that still need clarification: 1) Market universe: Do you want all U.S. common stocks (≈4,000 names) or another universe (e.g., only S&P 500 constituents)? 2) Rebalancing mechanics: Ranking date – use yesterday’s close (so we buy next-day open) or today’s open? Weighting – equal weight for each of the 500 names, or volume-weighted / cap-weighted? 3) Price type: is "open-to-next-day-close" acceptable for the 1-day holding period? 4) Basket handling: the platform’s built-in back-test engine works ticker-by-ticker. To evaluate a 500-stock basket we need to build a synthetic portfolio (equal-weight index) and then back-test that index. I can script that, but it will involve an extra data-processing step outside the one-ticker engine. Is that acceptable? Please let me know (or feel free to simplify the request, e.g., analyse the S&P 500 equal-weight ETF "RSP" as a proxy).