THERE has been a lot of chatter about the K-shaped economy. A yawning gap exists between high earners who are spending and growing their wealth, and low-income households who have to live from hand to mouth. The K-shaped economy may also be evident at the corporate level, in which rich companies expand rapidly, while smaller businesses struggle to pay their bills. Many consumer-facing businesses have been highlighting what they see as a bifurcated economy. Airlines, for instance, have talked about a growing demand for seats at the front of the plane, while some budget airlines have faced problems attracting passengers. Fast-food restaurants have been forced to introduce more affordable items into their menus, while many fine-dining restaurants appear to be unaffected. The K-shaped economy has not been lost on the US Federal Reserve. Last year, it said many consumers at the lower end are struggling, and that they are buying less and shifting to lower-cost products....