A "sale" is a necessary pre-condition to application of the first-sale doctrine, but that does not imply that exhaustion of copyright is a necessary pre-condition to the existence of a "sale." The Copyright Office's official position is that first-sale doctrine does not apply to digital sales, not because they are not "sales," but because they necessarily involve creating a copy of the digital item--unlike the sale of a physical item. The Copyright Office and USPTO has stated that digital sales do not meet key assumptions underlying the first-sale doctrine: there is no tangible good that can be owned by only one person at a time that is subject to wearing out.