The sum total of those investments in infrastructure and supply chain management have made Amazon by far the most valuable retailer in the United States. Amazon's $356 billion valuation is so big, it's larger than Wal-Mart, Target, Best Buy, Macy's, Kohl's, JCPenney, and Sears combined. With the recent acquisition of Whole Foods, there are no signs the retailer has any plans of slowing down.To help those shipments leave the warehouses on time, Amazon relies on a growing fleet of autonomous robots that fetch packages from their shelves and bring them to human employees. The 45,000 robots live across 20 fulfillment centers in the US. In 2016, the company increased the fleet 50% from its prior head count of 30,000.A back-of-the-envelope calculation reveals all those packages (not including padded envelopes) yield roughly 26,400 square miles of cardboard. The total land area of West Virginia, meanwhile, is just north of 24,000 square miles. Given the speed of Amazon's shipments, the company could blanket the whole US in cardboard in about five months.Amazon fulfillment is a beast of its own. A report from 2013 (the latest year for which data are available) found Amazon shipped 608 million packages that year, or 1.6 million packages a day. As of 2015, Amazon estimated its fulfillment centers were within 20 miles of 31% of the US population, and within 20 miles of 50-65% of its core, same-day-accessible market.Speaking of Amazon Prime, the company now counts approximately 63 million people among its subscriber base, or about 25% of the total US adult population. That number may underestimate the true coverage, however, since it doesn't account for multiple adults in one household all sharing the same Prime account.Amazon used to be a way to buy books online; today, it's the default buying site for just about everything, especially for people who have Amazon Prime. An analysis by Slice Intelligence released in February found that 43% of all US online retail sales were done through Amazon in 2016. That's up from 33% in 2015 and 25% in 2012.Amazon has more than 300,000 employees worldwide, and 40,000 in Seattle alone. As a portion of the city's working-age population — roughly 528,000 — that comes out to 7.5% of the city working at Amazon. For perspective, if the same portion of New York City's adults worked for one company, that company would have about 488,000 locals on staff.