U.S. warehouses have added 262,000 jobs over the past five years as retailers ramp up the capacity to distribute the growing number of goods bought online by American shoppers. The Wall Street Journal calls these jobs, which largely involve "picking" items from warehouse shelves and packing them in boxes, "the biggest labor cost in most e-commerce distribution centers, and among the least automated."

The problem of creating a robot that can grip and pick up almost any object, and put it in a box, has vexed the industry: such a robot, if it replaces workers doing the same job, could cut a fifth of the cost of filling e-commerce orders, MWPVL International's Marc Wulfraat tells the WSJ. As it stands, warehouses are having trouble filling jobs amid a tight labor market and rising wage demands.

Why it matters: Such robots could help online retailers by putting a lid on wage growth, giving them an alternative to meeting demands for higher pay.

• That is not good news for workers, though: wages have remained stagnant since the financial crash, and — should robots take more jobs in warehouses — they would both keep that cap on pay, and cut off a source of jobs for laid-off retail workers.