China’s rapid credit expansion is worrying. Will Chinese policymakers be able to contain the growth of credit without undermining economic growth and without triggering a banking or currency crisis? Aside from the consequences of Brexit, this is probably the most important issue facing global policymakers and investors today.

As it turns out, there are powerful arguments on both sides. The positives—high national savings and returns to investment, combined with the government’s broad tools for intervention—must be measured against a set of negatives—growing loan losses, the spread of shadow banking, large capital outflows, falling investment returns, and declining confidence in the government’s financial policy management. Against this complex background, it is no wonder that concerns and uncertainty are both high. What one can say confidently remains conditional:  things are very likely to end badly if the credit buildup continues amid slowing economic growth...