Prerequisite to understand global economic activity, CB set IR's, debt, QE, & resultant asset prices. Quick demographic tutorial.
Below, global 15-35yr/old females, annual births, and post childbearing 35+yr/old females...plus likely actual births vs. UN medium variant data.

But to gauge the impact of population change on economic activity (& the motivating factor behind .Gov and CB reactions)...break it down by ave. income per group.
High Income=$45k, China=$10k, Upper Middle (x-China)=$9k, Lower middle=$2k, Lowest Income=$820.

But a quick check of the groupings that do 80%+ of the consumption, have 80%+ of income, savings, access to credit...and the group the lower income nations are dependent upon for exporting their way to higher incomes...Again, 15-35yr/old childbearing and births.

Change per period in consumer nations 15-35yr/old females...total & %

Change per period in consumer nations births (as above, these #'s are inclusive of ongoing rates of immigration & immigrant births).

To highlight the deceleration and transfer of pop. growth from high to low income nations (inclusive of ongoing est.'s of immigration/immigrant births)...check changing 15-35yr/old females/births by period.

To wrap, annual change in births incl. income groups...& the same multiplied by GNI per capita of each grouping to highlight the overweighting of growth among wealthy...& shift to synthetic growth (ZIRP, QE, Deficit) to mask declining organic growth.

When speaking of economic growth and asset valuations, consider that against the foundation that is consumer nations childbearing females, births.