IDEXX Plummets 3.27% Amid Unexplained Selloff, Dollar Volume Ranking Falls to 364th

IDEXX Laboratories (IDXX) closed 3.27% lower on Sept. 24, 2025, with a trading volume of $0.27 billion, ranking it 364th in dollar volume among U.S. stocks. The decline marked a significant drop from its recent performance, though no direct catalysts were immediately disclosed in accessible reporting.

Analysts noted the stock's movement aligned with broader sector pressures but lacked specific event-driven triggers. Institutional activity remained subdued, with no major buy or sell orders reported through standard tracking channels. The company's guidance and operational updates had not yet been revised in the preceding weeks, suggesting the sell-off may have been algorithmic or speculative in nature.

Backtesting of a hypothetical "Top-500-by-volume" portfolio from Jan. 1, 2022, to Sept. 24, 2025, would require constructing a synthetic index of equal-weighted daily constituents. This process involves aggregating intraday volume data for U.S.-listed stocks, calculating daily average dollar volumes, and rebalancing the basket accordingly. Key parameters include execution at next-day open prices, zero transaction costs, and no risk controls, creating a pure buy-and-sell strategy. The methodology remains pending confirmation of rebalancing logic—whether based on average daily volume (ADV) or single-day share volume—before generating the final synthetic time series for evaluation.