The probe was technically and legally complex, examining whether a decades-old tradition of releasing data such as job totals and economic growth through a select group of media companies could be manipulated via new technology.

WSJ: U.S. Probed Media Firms on Data Reporting

The FTC's probe is still at an early stage, with investigators seeking to learn the inner workings of a complex business.

WSJ: FTC Focuses Google Probe on Android, Web Search