I obviously haven’t been keeping up with the local economic scene, because it came as a complete surprise to discover that the key to our future prosperity was something called the “low-altitude economy.” Apparently this idea has been around for some time. It was mentioned in the national government’s work report and subsequently endorsed (surprise!) by our chief executive. What is it? I wondered if it was one of those metaphors dear to economists, like “inflation” or “depression.” But it doesn’t sound very inspiring: a bit too reminiscent of a low-rent flat, or a low-energy boyfriend. Or was …