&gt; Barring some science fiction scenarios, fertility has dropped below replacement and is of a nature where it never truly rises.<p>Its dropped because of shifting economic incentives. Its pretty simple to shift those incentives to shift it back the other way to some degree (and almost certain to happen if, for an extended period of time, the developed world sees negative overall growth counting both natural growth and immigration.)<p>&gt; You can disagree, almost everyone does. But the implications of disagreement are bizarre, you must imagine some future where all 5th generation-only children wake up and say &quot;I want 2.1 children&quot; or 10 percent of those 5th generation children wake up and say &quot;I want 20 children&quot;.<p>No, I just imagine a future where policymakers -- having known for generations the policy factors which promote low birth rate -- look at the situation in their countries, recognize that negative natural growth is no longer being offset by immigration, tweak the policies so that reproduction is more incentivized, resulting in the overall growth rate rising out of negative territory. Its not people magically waking up with different preferences, its people reacting to different situations with different policies and changing the payoff matrices people face in society with the <i>same</i> preferences.