Was one in 20 this time last year.
UK bookie William Hill says its users are increasingly going mobile, and that this past weekend it expected new records - thanks to the Derby and an England football friendly.
The William Hill App was downloaded over 26,000 times on Grand National Day (April 14th). And that meant that more than 1,000 bets per minute were taken on the biggest race of the year.
For the Derby, William Hill was expecting 800 per minute.
The firm now believes there will come a day in the next two years when half the non-cash bets taken will be on mobile.
Kate Miller, PR director at William Hill said, "There has been phenomenal growth through our mobile channel in recent months, with our industry leading app taking centre stage.
"From a betting and business perspective, mobile is the primary entry point to the next generation and William Hill are again proving the number one player in this sector."