TransUnion’s $1.2B Volume Surge and 10.64% Plunge: Regulatory Scrutiny Drives Volatility Amid 85th Ranking

On October 2, 2025, TransUnion (TRU) saw a significant 122.13% surge in trading volume to $1.2 billion, ranking it 85th among the day’s most actively traded stocks. However, the shares closed 10.64% lower, reflecting heightened market volatility.

Recent developments highlight regulatory scrutiny as a key driver. U.S. regulators are reportedly investigating TransUnion’s data-sharing practices with third-party lenders, raising concerns over potential compliance risks. Analysts note the probe could impact the credit bureau’s partnerships and revenue streams, though no formal charges have been announced. The stock’s sharp volume spike suggests increased short-term speculation amid uncertainty.

Operational updates also drew attention. TransUnion announced expanded data partnerships with regional financial institutions, aiming to enhance its market reach. While this could bolster long-term growth, investors remain cautious about near-term execution risks and margin pressures from rising compliance costs. The mixed signals contributed to the stock’s bearish close.

To build an accurate back-test, I need to pin down a few practical details about the trading universe and trading mechanics: 1. Stock universe • Do we screen the entire U.S. equity market (e.g., all listed common stocks) or a specific subset such as the Russell 3000 or S&P 500 constituents? 2. Ranking and trade timing • Should the ranking be based on yesterday’s total dollar volume (close-to-close) and trades executed at today’s open, then liquidated at today’s close? • Or do we rank on today’s volume at the close, buy at the next day’s open and sell that day’s close? 3. Position sizing and transaction costs • Equal-weight each of the 500 names each day? • Any commission/slippage assumptions? 4. Price data preference • Use open-to-close returns (buy at open, sell at close) or close-to-close (buy at one close, sell next close)? Please let me know your preferences (or accept sensible defaults) and I’ll generate the corresponding back-test.