At an Amazon sellers’ workshop, the instructor told us 90% of Amazon selling happens on mobile. Am I the only guy who has bought and continues to buy 90% of Amazon stuff from my laptop?

No. You’re NOT the only one.

I haven’t kept a count but ~25% of my Amazon orders are “showrooming”, so, by definition, mobile e.g. https://gtm360.com/blog/2018/11/09/discount-is-not-the-only-reason-for-shopping-online/. But the balance 75% are definitely from laptop / desktop.

That said, I wouldn’t rush to debunk the instructor’s statement. In general, I’ve noticed that language plays a very important role in digital operating models. This could just be another example where nuance is involved. 

“Selling” could mean “sales”, in which case the statement “90% of selling happens on mobile” can be true only if 90% of buying happens on mobile. I don’t believe that’s the case.

OTOH, “selling” could also mean the activity carried out by Amazon Sellers viz. listing, price changes, updating inventory, etc. I’ve observed 3-4 Amazon Sellers up close. They use mobile 100% of the time. I can easily believe that “90% of Amazon selling happens on mobile” even if <<90% of Amazon buying happens on mobile.

Then there’s also the attribution problem, famously exemplified by Myntra’s decision to kill, and then revive its website. 90% of orders came via Mobile, so company killed website. Then found sales plunging. On deeper analysis, it found that that 90% of the click of the ORDER button happened on Mobile. But many prior stages of the Customer Journey such as browse, compare price, add to shopping cart, etc. actually happened on Desktop. So, going by “last click attribution”, the statement “90% on Mobile” was correct; but going by “end to end attribution”, the statement was wrong. More at https://gtm360.com/blog/2015/09/04/teardown-of-myntras-app-mantra/. 

Who knows, a similar misattribution problem could be in play even in the case of “Amazon selling”, whichever way it’s defined.