The US Consumer Price Index surged in April, topping estimates by a wide margin. The question is whether this is the start of an inflationary wave or just the latest run of noise? Reliably answering that question will take several months at the least, but if we ignore that caveat the numbers for last month certainly look worrisome. Let’s start with core CPI, which strips out the food and energy noise, a filter that helps identify the underlying trend.