Brian Wieser, of Pivotal Research Group, pointed out in a note for clients that Facebook says it can reach 41m 18-24 year-olds in the US, whereas official census data show there were only 31m people of that age group last year.
Similarly, Facebook claims a potential reach of 60m among 25-34 year-olds, but census data counted just 45m people within that age range, CNBC reported.
“Specifically, through Facebook's Ads Manager we can see that Facebook claims a potential reach within the US of 41m 18-24 year-olds, 60m 25-34 year-olds and 61m 35-49 year-olds,” Wieser wrote.
“By contrast, US Census data indicates that last year there are a total of 31m 18-24 year-olds, 45m 25-34 year-olds and 61m 35-49 year-olds,” he added.
“Conversations with agency executives on this topic indicate to us that the gap between Facebook and Census figures is not widely known.”
Facebook was forced to admit errors in some of its metrics at the end of last year and launched a blog called Metrics FYI to share corrections with advertisers. It also agreed earlier this year to have its metrics audited by the US Media Rating Council.
However, in response to Wieser’s observation, the company indicated that its reach estimates took in a range of factors beyond the raw census data.
“Reach estimations are based on a number of factors, including Facebook user behaviors, user demographics, location data from devices, and other factors,” Facebook 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.”
But in another development, Fortune magazine checked Facebook’s reach metrics for the UK and Canada and compared the results with census data in the two countries.
According to Fortune, Facebook promises it could reach a potential 5.8m 20-24 year-olds in the UK as well as 6.4m 25-29 year-olds and 5.2m 30-34 year olds.
But when the last census was conducted in 2011, the UK had only 4.3m 20-24 year-olds, 4.3m 25-29 year-olds and 4.1m 30-34 year olds.
And looking at Facebook’s claims for Canada, Fortune said it reached 3.2m 20-24 year-olds and 3.4m 25-29 year-olds, whereas the Canadian census data showed 2.2m and 2.3m respectively for each age group.
Data sourced from CNBC, Fortune; additional content by WARC staff