New Delhi, Sept. 25 -- As countries stare at the prospect of slower economic growth in the post-Trumpian world, the Keynesian answer of fiscal support-financed through additional public debt-is a vanishing option, given the reality of payback burdens reaching unsustainable levels.

Ironically, it is not the usual suspects that are guilty of living far beyond their means by taking the easy way out of borrowing more. More than emerging-market economies, it is advanced countries-the US, UK, Germany and France, to name a few-that are struggling with rising debt and its corollary, higher interest payments.

Unfortunately, debt-financed spending is one of the easiest options for fiscal authorities to tackle growth slowdowns. But it comes at a c...