[jyl]

350, see my edit to the preceding post - I tried to explain my views a little more clearly.

Yes, if everything else was unchanged I think it would be desirable to have population peak out at less that 9 billion. But all other things won't be unchanged - there will be tradeoffs. Would it be better to have (1) a very rapidly aging population whose growth rate slows very rapidly, so that global poplation peaks out at, say, 7 billion, or (2) a gradually aging population whose growth rate slows gradually, so that global population peaks out at 9 billion?

I think that's actually not an easy question. The measures you would have to take to very rapidly slow population growth might not be feasible, or might be pretty extreme. The strain on societies of "suddenly" slowing population growth and "suddenly" aging the population might be pretty bad.

I need to do some more thinking and reading about this myself. But honestly, it's not the highest priority for me, because there's very little I can do about it - even if I could single-handedly choose the next President, he won't be able to do much about it.