Charts are pretty self explanatory. Total energy consumption of nations / groupings of nations vs. their core (25-54yr/old) employed populations and total core (25-54yr/old) populations. BTW- I think the change in energy consumption is a pretty good tell for actual economic activity and growth.
Below, total US energy consumption (quadrillion BTU's) vs. core employees. Correlation? Causation? Anyway, just is what it is.
Below, same as above but added core population through 2025 (UN assumes, perhaps wrongly, continued levels of immigration to achieve that slight population growth).
Below, same as the above, but with core population through 2030...by 2030, there will be fewer in the core population than are total core employees now. For a highly levered economy, disaster.