Ridding says the data-driven approach is transforming its marketing and advertising, too. The data collected from registrants allows advertisers to target campaigns to, say, executives in the U.S. aerospace industry, or HR department heads in India.

And, this sounds lucrative, or creepy, depending on your mood:

Added to this is a proprietary reporting tool called Deep View, which offers “the most” insight into advertising campaigns and how they perform compared to its competitors’, the FT says. (One media buying manager we spoke to confirmed this assessment, noting it is only available for direct, and not programmatic, ad buys.) During and after campaigns, advertisers can see who has seen or clicked on a campaign, and the optional placement and time of days to run the ads, “giving them the option to reassess mid-campaign, switch creative and retarget,” a spokesperson explains.

Sadly few figures are provided here, either.

The good news is that, according to public filings, overall revenue in the group since 2008 (which, again, includes sizable non-FT units) was up 13.6 percent at the end of last year, to about $669 million (£443 million), while profitability (after accounting for the sale of a unit) is more or less steady, at about $74 million (£49 million).

On the other hand, Ridding tells us, overall ads (print and digital) now make up only 39 percent of the FT Group’s revenue, as opposed to 52 percent in 2008.

So what we do know is that, even with “Deep View” and everything else the FT is able to sell to advertisers, the real growth is coming from digital subscriptions, not digital ads.

And what we don’t know about digital ads’ performance and prospects is a lot.

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Dean Starkman Dean Starkman runs The Audit, CJR's business section, and is the author of The Watchdog That Didn't Bark: The Financial Crisis and the Disappearance of Investigative Journalism (Columbia University Press, January 2014). Follow Dean on Twitter: @deanstarkman.