Carmax Trading Volume Surges 296.6 to $1.29 Billion as Stock Plummets 20.07 Despite Ranking 67th in Market Liquidity

On September 25, 2025, Carmax (KMX) recorded a trading volume of $1.29 billion, marking a 296.6% surge from the previous day and securing the 67th highest volume position among listed stocks. Despite the robust liquidity, the stock closed with a 20.07% decline.

Recent developments highlight heightened market scrutiny over Carmax's business model amid evolving consumer preferences in the automotive retail sector. Analysts noted that the sharp drop in share price could be attributed to broader sector concerns rather than company-specific issues, as investors recalibrate expectations for used vehicle pricing trends and operational margins. The stock's volatility underscores its sensitivity to macroeconomic signals and industry-wide regulatory shifts.

To ensure I set up your backtest correctly, could you please confirm a few points? Market universe: Should we consider U.S. listed stocks only, or a different market? Weighting method: Should the strategy allocate equal weight to each of the 500 stocks selected each day? Data availability: At the moment, our back-testing engine evaluates one ticker at a time. For a portfolio that re-selects 500 names daily we would need to aggregate multiple tickers, which isn’t supported directly.

One workaround is to use a proxy—e.g., an ETF that tracks high-volume stocks—or we can focus on a single stock for illustration. If you’d like the full multi-stock simulation, I can export the selection logic and performance calculation for you offline. Let me know which option you prefer, or if you have an alternative in mind.