Seattle startup Placed tracks in-store foot traffic and we now have a better idea of which wireless carriers saw the most customers this holiday season.

For the past six weeks, Verizon and AT&T went back and forth for the most-visited store, with AT&T holding the lead for four weeks. T-Mobile ranked fourth behind Sprint for much of the holidays, but made a late surge in December.

To collect data, Placed used its location-based Placed Panels platform that lets marketers create a unique panel for their company for free and recruit participants, to analyze the places they visit and better understand customer behavior.

Earlier this month, Placed introduced a new service called Give 2 Charity. Users install the app, grant it location permissions and then choose a charity to donate to after racking up enough points.

We wrote about Placed back in June, with CEO David Shim telling us at the time that the service allowed app developers to see where people are consuming content. Measured locations are aggregated across thousands of users to provide analytics to third parties.

Placed expanded its location analytics in August and raised $3.4 million from Madrona Venture Group and others in March.

Previously on GeekWire: Giving back made easy: New Placed app lets you donate to charity by installing app

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