Amazon, Walmart, and Best Buy quietly entered an (almost) $4T industry--and the big winner is obvious

Amazon, Walmart, and Best Buy are three of the biggest names in retail. And despite the ruthless competitive nature of their relationship, all three are currently thriving. But over the past few years, each of these companies has been planning to venture into a completely new industry, one that's worth almost four trillion dollars and is inviting disruption: It's the health care industry.