Imagine piloting a speeding jumbo jet half-blindfolded, relying on wildly inaccurate instruments and controls that respond sluggishly, if at all. That is the daily challenge confronting China’s economic managers. It is a tribute to their skill that, despite turbulent patches, they have so far kept the economy airborne and broadly on the right flight path.

Economic policymaking is inherently more of an art than a science. In China, it verges on black magic. Not only are policy instruments crude; decisions have to be based on shaky, confusing and sometimes non-existent information.