Procter & Gamble Co. has been vigorously rooting out fraud and unverified data from its digital buys while also doing more influencer marketing, but those two things may be at cross purposes. In a new study, two P&G brands last month ranked among the top 10 in using paid influencers with fake followers.

The data, which comes from Points North Group, shows that Pampers and Olay ranked No. 4 and 10, respectively, on the list of brands with the most fake followers among their paid influencers last month; Pampers with 32 percent and Olay with 19 percenty. Topping the study's list: Ritz-Carlton, with a whopping 78 percent of fake followers for its influencers.

Ritz-Carlton didn't respond to requests for comment. P&G spokeswoman Tressie Rose declined to comment on report specifics, since the company hasn't seen the data and isn't familiar with Points North or its methodology. "There are a lot of companies out ther offering services to combat this," she says. "Bot fraud is an industry-wide issue and one we're continuing to actively work on."

Even as use of influencer marketing by big marketers grows, so do questions about how it's measured. Reach numbers used to measure influencer campaigns often come from raw follower counts, without regard to how many followers actually saw posts—or were real.

Numbers marketers usually get on influencer campaigns come either from their influencers or third-party providers "grading their own homework," as Points North co-founder Peter Storck sees it. He's now working with clients, whom he says he doesn't yet have approval to name, to help "get real measures of their influencer marketing, because they don't get them from the partners they work with."

Points North is a firm founded by former executives with analytics experience going back to the old Jupiter Research digital ad measurement business, as well as with the Word of Mouth Marketing Association (now part of the Association of National Advertisers) and such influencer networks as CrowdTap and House Party. Storck joined co-founder Sean Spielberg, who was with Crowdtap, to form what Storck calls "the Nielsen of influencer marketing."

Storck says he's unaware of any other third-party audience measurement dedicated to influencers space, though some firms have sought out third-party validation of their reach numbers other ways. Cincinnati-based Ahalogy, for example, only charges clients for digital impressions verified by Oracle's Moat on content created by its influencers.

Points North is releasing its first public data in the form of lists of the biggest spenders on influencer marketing in March, the most efficient spenders based on cost per thousand impressions (CPM), and those with the most fake followers. Storck says work for private clients has included a large cosmetics brand where $600,000 out of a $2 million outlay for influencers was for impressions that weren't seen or were seen by fake followers.

The spending data is based on analysis of influencers used by brands and industry norms on payments, which Points North founders say average 0.3 cents per follower per post across the industry based on their prior sell-side experience and more recent input from clients. It's an estimate, but one they say they're looking to apply consistently.

Fake follower counts are based on Points North scanning followers of influencers to sort out such things as accounts making comments in languages that don't make sense for the content or the influencer, or accounts making the exact same comments across multiple influencers and posts. Storck says the algorithm is similar to what e-mail users lean on to sort out spam.

The CPMs are based on the spending estimates and effective reach, which not only subtracts fake followers, but also uses estimates of how many legitimate followers actually see posts, leaning on engagement rates for posts and norms for viewership gleaned from actual influencers, who get such information from their own Instagram business accounts, for example.

The top influencer spenders last month, as estimated by Points North, include names you've likely heard of, such as Amazon, Walmart and Mercedes Benz, but also the more obscure—at least until that influencer spending kicks in—like Flat Tummy, Waist Gang Society and SugarBearHair vitamins.

Among the most efficient spenders was Heinz Ketchup, owned by the Kraft Heinz and the ever-thrifty 3G Capital; Ulta Beauty; and Clorox Co.'s Hidden Valley, all with CPMs around $2 or less.

P&G also had a brand on the top 10 most efficient, Vicks.

Below, top spenders, most efficient, and most fake followers.