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TMUS −12.3%: one of its biggest daily moves this year. T-Mobile US, Inc. moved 11.4 points less than its sector, on 1.8× its usual volume.

2026-10-09 · TMUS

TMUS −12.3%: one of its biggest daily moves this year

T-Mobile US, Inc. moved 11.4 points less than its sector, on 1.8× its usual volume.

The story in plain words

Friday, October 9, 2026. TMUS −12.3%: one of its biggest daily moves this year. T-Mobile US, Inc. moved 11.4 points less than its sector, on 1.8× its usual volume.

What the data shows for T-Mobile US (TMUS): TMUS −12.3% today. Its sector fund (XLC) −0.9% today. S&P 500 (SPY) +0.5% today.

Worked out from that data: 11.4 points less than its sector. Volume 1.8× its 20-day average. Its biggest daily move in the past 250 trading days. After the 5 most similar TMUS days since Oct 21, 2021, the stock was higher 5 days later 5 of 5 times (History, not a forecast).

Possible contributors. These line up in time with the move; they are not confirmed causes: News: “Crown Castle Soars 13% as SpaceX’s $8 Billion Spectrum Buy Keeps Tower Build Option “Very Much Alive”” (Published around the move. Timing only, not a confirmed cause). News: “What SpaceX’s Spectrum Buy Says About a Starlink Mobile Network” (Published around the move. Timing only, not a confirmed cause).

About the company: T-Mobile US trades as TMUS and is part of the S&P 500, in the Communication Services sector (Wireless Telecommunication Services), headquartered in Bellevue, Washington, founded in 1994.

This is one of CookieStocks’ daily stock stories about unusually large one-day price moves in S&P 500 stocks, measured against each stock’s own history, its sector and its usual volume. Stories are found automatically each trading day from market data and SEC filings, and every claim is labelled as observed, calculated or a possible contributor. Statistics only, not investment advice.

Prove it

Every claim on the graphic, labelled: observed (straight from the data), calculated (worked out from it), or possible contributor (lines up in time, not a confirmed cause).

  • OBSERVED
    TMUS −12.3% todayOct 9, 2026, 12:35 PM ET
  • OBSERVED
    Its sector fund (XLC) −0.9% todayOct 9, 2026, 12:35 PM ET
  • CALCULATED
    11.4 points less than its sectorHow: stock return − sector fund return · Oct 9, 2026, 12:35 PM ET
  • OBSERVED
    S&P 500 (SPY) +0.5% todayOct 9, 2026, 12:35 PM ET
  • CALCULATED
    Volume 1.8× its 20-day averageHow: today’s volume ÷ average of the last 20 days · Oct 9, 2026, 12:35 PM ET
  • CALCULATED
    Its biggest daily move in the past 250 trading daysHow: share of past daily moves smaller in size · Oct 9, 2026, 12:35 PM ET
  • POSSIBLE CONTRIBUTOR
    News: “Crown Castle Soars 13% as SpaceX’s $8 Billion Spectrum Buy Keeps Tower Build Option “Very Much Alive””Published around the move. Timing only, not a confirmed cause. · Oct 9, 2026, 11:34 AM ET
  • POSSIBLE CONTRIBUTOR
    News: “What SpaceX’s Spectrum Buy Says About a Starlink Mobile Network”Published around the move. Timing only, not a confirmed cause. · Oct 9, 2026, 10:37 AM ET
  • CALCULATED
    After the 5 most similar TMUS days since Oct 21, 2021, the stock was higher 5 days later 5 of 5 timesHistory, not a forecast. · How: same-company days with a move of similar size and direction

T-Mobile US (TMUS) financials and filings →

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Statistics only, not investment advice. Past moves don’t predict future ones. Data as of Oct 9, 2026, 12:35 PM ET.