Is this why budget deficits might prove sustainable?

By Adrien Auclert, Hannes Malmberg, Frederic Martenet, and Matthew Rognlie:

We use a shift-share approach to quantify the general equilibrium effects of population aging on wealth accumulation, real interest rates, and capital flows. Combining population projections with household survey data from the US and 24 other countries,we project the evolution of wealth-to-GDP ratios by changing the age distribution,holding life-cycle asset and income profiles constant. We find that this compositional effect of aging is large and heterogeneous across countries, ranging from 85 percent-age points in Japan to 310 percentage points in India over the rest of the twenty-first century. In a general equilibrium overlapping generations model, our shift-share provides a very good approximation to the evolution of the wealth-to-GDP ratio due to demographic change when interest rates remain constant. In an integrated world economy, aging generates large global imbalances in the twenty-first century, pushing net foreign asset positions to levels several times larger than those observed until today.

Via Steven Bogden.  This is very likely an important piece.