No difficult economic terms, no tough charts, just simple math.
1 - The world's population of under 40 year olds (excluding Africa) has essentially peaked (chart below - bars represent 0-40yr/old population, dashed lines UN future estimates). What is interesting about the under 40 year old population is that they are responsible for about 97% of all pregnancies / births. It's not impossible for 40+ year old women to have children, just statistically very rare (particularly outside the developed world).
Ok, we've established the global under 40 population (excluding Africa) has essentially peaked. Now we lay out the chart below that a shrinking population (above) isn't replacing themselves. The chart below shows world fertility rates, again breaking world fertility (ex-Africa) from the African fertility rate. The world (ex-Africa) has fallen below the 2.1 births per female replacement level...and even Africa is rapidly slowing.
A flat to shrinking child bearing population that is not reproducing at a rate to replace themselves and the fertility rates continue to fall. This all points to the potential the low UN 0-40yr/old population estimate could be fairly accurate (chart 1, lower bound). With either the medium or low estimate, the UN is telling us they expect a massive depopulation of under 40 year olds world-over. Somewhere between 1 to 2.5 billion fewer by 2100 & perhaps well in excess of a 50% decline (except for Africa?). I lay out why the Ex-Africa approach to viewing global economics makes sense, HERE.
All the interest rate cuts and debt has been undertaken under the paradigm that it would be more easily repaid in the future...but now we've come to "the future" where there are fewer of us to service the debt, buy homes, buy cars, consume our way to prosperity...or pay the taxes to keep the social systems solvent. Basically, we are doing our best Wile E. Coyote impression - we've gone over the cliff but somehow haven't realized it quite yet. What this has looked like in the US and globally, HERE.
Of course, the flipside is the 40+ year old world (ex-Africa) population is set to continue soaring (chart below). Unfortunately, by age 65, the population consumes at about 70% of its peak earning years and by 75, consumption falls to somewhere around 50-60%. The elderly are credit averse, have made their major life purchases and spending (kids, homes, college) and turn to net sellers in retirement.
Absent a growing population of young to buy their assets (IRAs, homes, etc.), we have a small problem (central bank asset purchases to the rescue). As for Africa, they generally represent about 5-10% of the consumption of the depopulating young around the world they are replacing. Global economic activity and consumption are likely to fall off a steep, high precipice.
The implications economically, financially, societally, etc. etc. of a collapsing population of young and soaring older population should be ringing alarm bells, but instead our politicians seem officially mindless (or intentionally misleading the populace) in the face of a cataclysmic shift.
Just to make the point here is what the shift looks like for the US. The breakdown in growth among 25-54yr/old employees (blue line) coinciding with interest rate cuts (black line) and massive federal debt increases (red line).
The chart below shows total federal debt apportioned per the nearly 100 million 25-54yr/old employees (red columns) vs. the non-growth in wages shown by the real median household income (green line).