The number's real but it's been mangled in the retelling, and the actual figures are worth having straight.
The Dutch regulator looked at 15,761 newly opened online accounts that had betting activity in May 2025 and tracked them for three months. Of those, 5,244 belonged to people aged 18 to 24. Within that group, 2,144 accounts — 41% — were held by 18-year-olds.
So it's not half of 18-year-olds signing up. It's that 41% of all the new accounts in the 18 to 24 bracket belonged to the very youngest year in it, which is a different claim and arguably a more striking one.
The birthday figure is 11% opened on the day itself. 38% within a month of turning 18.