Facebook says it can reach 25 million more people in the US than census data shows exist (FB)

Facebook tells advertisers that it can reach 25 million more people in the US than census data shows existed in 2016, according to Pivotal Research Group analyst Brian Wieser.

Wieser highlighted the apparent discrepancy between Facebook's ad manager for marketers and US census figures in a note distributed to clients on Tuesday. The bearish Facebook analyst said the discovery "could restrain Facebook’s growth in video ad sales" as the company pushes into distributing premium, episodic shows.

Facebook's ad manager says the social network can reach 41 million 18-24 year-olds, 60 million 25-34 year-olds, and 61 million 35-49 year-olds, according to Wieser. Meanwhile, US census data from 2016 indicates that there are 31 million 18-24 year-olds, 45 million 25-34 year-olds, and 61 million 35-49 year-olds living in the country. Nielsen has predicted the numbers to remain mostly unchanged for 2017.

A Facebook spokesperson told Business Insider on Wednesday that the company's ad reach estimations are "not designed to match population or census estimates" but rather "how many people in a given area are eligible to see an ad a business might run."

“Reach estimations are based on a number of factors, including Facebook user behaviors, user demographics, location data from devices, and other factors," the spokesperson said in a statement. "They are designed to estimate how many people in a given area are eligible to see an ad a business might run. They are not designed to match population or census estimates. We are always working to improve our estimates.”

Facebook's projected reach has no effect on the delivery and billing of ads, the spokesperson added.

The spokesperson also said that Facebook's age data is self-reported and includes non-residents like travelers. There were nearly 76 million visits to the US in 2016, according to the US office of travel and tourism. Meanwhile, roughly 67 million US citizens traveled out of the country last year.

The discrepancy highlights the pressure Facebook is under after the nearly one dozen metric errors the company reported over the past year. In February, Facebook said it would submit to an audit of its ad metrics by the Media Rating Council.