According to a recent report in the Seattle Times, in 2016 Amazon significantly expanded the deployment of Kiva Robots in their fulfillment centers. Amazon acquired Kiva Systems in 2012 and the robots automate the picking and packing process. According to the report, Amazon has 45,000 robots deployed across 20 fulfillment centers which represents a 50% increase over the previous year and a 200% increase since 2014. Since 2014 the human workforce has increased by roughly 100%.
You will find more statistics at Statista
Since the robots have only been in use for a few years, it’s premature to draw a direct correlation between the growth of the human and robot workforce, but is something to keep an eye on. In 2014, for every robot at Amazon there were 10.27 human workers and just two years later there were 6.82 human workers for every robot. Again, it is far too early to make a direct correlation but I think it’s fair to make an assumption that a trend is developing.
It’s also important to note that human workers still do the actual picking of pieces from shelving as the robots have trouble picking products of unpredictable sizes.
The next generation of robots, however, will incorporate advances in deep learning - the algorithms that powered Google's AlphaGo to defeat the world champion Go Player Lee Sedol - to identify products, pattern-match the size and weight and then identify the most optimal strategy to pick, pack, and ship. Amazon also hosts an annual robotic picking challenge where robots perform real-world tasks of picking orders and restocking shelving. In the 2015 competition, the best robots were picking at a speed of 30 items per hour (very slow compared to humans). In 2016, however, in a much tougher competition the robots were picking roughly three times faster at 100 items per hour. And even though it’s probably still a few years off before the speed and accuracy are on par with humans, the future is clear and it will be interesting to see the impact on the growth of human versus robot workforce.