A new survey suggests the Netherlands online gambling market could be significantly larger than previous estimates.

The survey, which was conducted by Motivaction on behalf of state-owned brick-and-mortar casino operator Holland Casino, suggests that as many as 1.5m Dutch adults gamble online, spending an average of €26 per month for a total annual spend of around €500m. Previous studies had suggested the market was worth closer to €300m per year.

Motivaction said its survey numbers indicate that around 700k Dutch adults indulge in games like bingo, poker, roulette, blackjack or sports betting via online sites three times or less per year, while another 800k partake four times or more.

Holland Casino suggested Motivaction’s numbers might actually undervalue the Dutch online market. The operator pointed to Denmark, which has a population one-third the size of the Netherlands, yet Danish online gambling revenue totaled €338m in just the first nine months of 2015. Extrapolating those numbers, Holland Casino suggests the Netherlands’ online market could be worth over €1b per year.