Thanks to Slice Intelligence (more on them below) we have a first estimate of how many Americans ordered Apple Watches Friday: 957,000 customers ordering an average of 1.3 Watches each, or a total of 1.2 million units.
I asked three analysts to extrapolate from that U.S. estimate to the rest of the world, and I got three different answers.
- Above Avalon’s Neil Cybart: “If the data is true, I would be surprised if total pre-orders weren’t at least 2-3 million across the nine countries over this past weekend. Of course, without knowing supply, it still remains tough to know how many of those will actually be shipped in April.
- Piper Jaffray’s Gene Munster: “If you take the Slice numbers as Gospel, it would imply 2.1 million worldwide. We’ve dialed that back to 1.5 million. We think some of the initial fanboy enthusiasm isn’t as intense outside the U.S.”
- Asymco’s Horace Dediu: “I found it fascinating that the store opened at a time when almost everybody in the U.S. and Europe was asleep and China was just about to start happy hour. Therefore I must assume that sales in China are higher than in the U.S. I don’t know how reliable Slice’s samples are, but if they are accurate then 2 million pre-orders seems a reasonable estimate.”
Where did Slice get its data? From consumers sufficiently enthusiastic about shopping to download Slice’s app and sign up for their free service. Here’s Slice’s pitch:
Slice keeps track of what you buy, effortlessly. The secret to the sauce is your email inbox. Just add the email account(s) where you send your merchant notifications, and we’ll do the work from there. Slice processes shopping-related emails (such as order confirmations, shipping notifications, and e-receipts from in-store purchases) to help you easily keep track of your stuff.
Here’s their video: It’s shopping smarter.
Today, according to Slice, their analytics engine has direct access to the electronic receipts of more than 2 million Americans. In their panel were 9,080 shoppers who ordered an Apple Watch on Friday. That’s where their estimate — 957,000 customers ordering 1.3 each — comes from.
Given Slice’s tilt toward heavy shoppers, their estimate could be high.
Follow Philip Elmer-DeWitt on Twitter at @philiped. Read his Apple (AAPL) coverage at fortune.com/ped or subscribe via his RSS feed.