While Facebook’s traffic is still growing, it was slower than usual due to a drop in membership in regions that adopted the services early.
According to figures from Inside Facebook, the company gained 11.8m more people in May, after a gain of 13.9m in April.
This compares to a gain of 20m new users, on average, in the past 12 months.
Inside Facebook believes that while the growth was mostly stimulated by regions late in adopting Facebook, regions where the service was already popular for a number of years saw a drop in membership.
The US lost 6m Facebook users, falling to 149.4m, and Canada’s Facebook membership dropped by 1.52m users.
The UK, Norway and Russia all posted losses of more than 100,000 Facebook users.
“If these countries – most of whom had adopted Facebook many years ago – had not lost users, and instead posted even small gains, Facebook would have had a much more typical month,” said Inside Facebook.
Inside Facebook noted that bugs in the Facebook advertising tool and seasonal changes, such as college graduation, could affect the figures.
However, it found that by the time Facebook membership reaches 50pc of the total population of a country, growth generally slows to a halt.
Regardless of this slowed growth, Facebook is still on track to reach 700m users soon, as it experienced 687m monthly active visits since the start of June.