In economies with excess productive capacity, targeted investment can yield a double benefit, generating short-run demand and boosting growth and productivity thereafter.

On their own, tariff and trade barriers, if viewed as transitory negotiating tactics, will not significantly change global investment patterns or the structure of global supply chains and employment.

Robotics has already made significant inroads in electronics assembly, with sewing trades - traditionally many countries' first entry point to the global trading system - likely to come next.

For highly indebted governments, low interest rates are critical to keep debt levels sustainable and ease pressure to restructure debt and recapitalize banks. The shift to a high sovereign-debt-yield equilibrium would make it impossible to achieve fiscal balance.

Productivity gains are vital to long-term growth because they typically translate into higher incomes, in turn boosting demand. That process takes time, of course - especially if, say, the initial recipients of increased income already have a high savings rate.