I'm at a bit of a loss as to what the 20 marker could possibly be for this topic ...
The Westergaard book has a sample Q on the ageing population, but this is given very little space in the textbook (perhaps it's given more attention in Browne?) so seems unlikely to be posed as a full essay question. On the previous spec, the essay questions that relate to this topic were all 'examine' rather than 'assess' questions and they were addressed to changes in the birth / death rate - I'm clear on how students would examine these issues, but less clear on how they would 'evaluate' (which is the stem for the new spec) such questions. There are no speciman questions / sample responses / mark schemes about this topic on the AQA website either.
I'd be massively grateful if you wouldn't mind sharing any thoughts about how potential demography questions might look or any additional AQA resources / examples of student work you may have on this as I'm seriously stumped!