https://www.cnbc.com/2018/11/04/amazon-could-soon-start-using-cubic-footage-to-measure-warehouse-space.html

As robots pack more and more items into Amazon's fulfillment centers, reaching high up on shelves to store and retrieve toiletries, electronics and household goods, the company is reconsidering how it accounts for space.

On last week's earnings call with analysts, Chief Financial Officer Brian Olsavsky said that Amazon could start using cubic feet, instead of square footage, to measure its warehouse footprint. That would change the measurement from one of sheer size to one of volume, and give a clearer picture of how Amazon is becoming more efficient as its inventory grows.