"Amazon seems to represent less than 10% of packages in the US [1]" No. They represent <10% of revenue for UPS, as the cite says. That gives you no info about

"Amazon seems to represent less than 10% of packages in the US [1]" No. They represent <10% of revenue for UPS, as the cite says. That gives you no info about the percent of packages for UPS, despite the quora claim. It's not safe to assume they pay what others pay, and in fact, given the range of volume discounts, it's entirely possible they pay 1/3rd-1/5th what others pay, if not less. (I base this on the fact that the companies i've worked for, which have nowhere near amazon's volume, seem to pay around that). If that was correct, they could represent 5-6% of revenues but 15-25% of volume. (it also tells you nothing about overall. It could be that combined across 6+ carriers, they represent a large percent of all package volume in the US).