The world’s largest e-commerce retailer said it employed 45,000 robots in some 20 fulfillment centers, The Seattle Times reported. That’s a 50% increase from last year’s holiday season, when the company had some 30,000 robots working alongside 230,000 humans. “We’ve changed, again, the automation, the size, the scale many times, and we continue to learn and grow there,” Amazon CFO Brian Olsavsky said of the robots in a conference call last April. The executive said he couldn’t point to any “general trends” in the adoption of robotics, because some fulfillment centers are clearly “fully outfitted” in robots and “some don’t for economic reasons — maybe the volume’s not perfect for robot volume.”