Guess which day is the most popular for buying pot in Washington state

Washington last month became the second US state to begin legal marijuana sales, and the state’s Liquor Control Board has tracked sales each day. Sales to date have topped $4.3 million and the data indicates that Friday is Washingtonians’ preferred day to shop for pot. About 25% of weekly sales occur on Fridays.

While this makes it appear that people simply are stocking up for the weekend, there are other factors at play. Stores in Washington have had a hard time keeping pot on their shelves. As a result, some are only transacting a few days a week—opening on a Thursday or Friday and selling out by Sunday. New stock comes in early the next week and the cycle repeats.

The way in which sales are reported to the state also is a factor. Mike Kashmar, chief financial officer for the Liquor Control Board, tells Quartz that while a majority of the state’s 22 pot stores report sales on a daily basis, some report less frequently, in some cases bunching several days’ sales together.