Dexcom Shares Fall 3 12% on Oppenheimer Downgrade as 320M Volume Surges 45% to 377th Market Activity Rank

On September 8, 2025, , , , . . The drop followed Oppenheimer’s downgrade of the stock to Perform from Outperform, citing growing competitive pressures. , signaling a reduced growth outlook. Analyst downgrades often trigger investor caution, leading to short-term sell-offs.

Recent momentum for Dexcom had been fueled by positive commentary from executives at the Wells Fargo Healthcare Conference four days earlier, . The company also noted expanded market access, with all three major (PBMs) now covering its non-insulin diabetes products. However, the latest downgrade appears to have tempered investor optimism, .

. , reflecting modest returns over five years. The stock’s volatility, , suggests market sentiment remains sensitive to catalysts. Analysts emphasize that while today’s move reflects the downgrade’s significance, it does not indicate a fundamental shift in the company’s long-term prospects.

To run this back-test accurately I need to clarify a few practical details about the strategy implementation:

1. Universe • Which market(s) should we draw the “top-500” list from (e.g., all NYSE + NASDAQ common stocks, only S&P 500 constituents, a different list)?

2. Ranking method & trade timing • Should the ranking be done each day using the prior day’s total dollar volume, then trade at the next day’s open and exit at that day’s close? • Or do you prefer buy at today’s close and sell at tomorrow’s close? (Please specify.)

3. Position sizing • Equal-weight each stock (1/500 per position) or weight by volume/market-cap, etc.?

4. Transaction costs / slippage • Do you want to assume zero costs, or apply a round-trip cost (e.g., 10 bps per trade)?

Let me know your preferences and I can prepare the data retrieval and run the back-test from 2022-01-03 through 2025-09-06 (latest trading day).