Thanks for writing this! For all the discussion that population growth/decline has gotten recently in EA(/-adjacent) circles, as a potential top cause area—to the point of PWI being founded and Elon Musk going on about it—there hasn’t been much in-depth assessment of the case for it, and I think this goes a fair way toward filling that gap.
One comment: you write that “[f]or a rebound [in population growth] to happen, we would only need a single human group satisfying the following two conditions: long-run above-replacement fertility, and a high enough “retention rate”, that is, a large enough fraction of the descendants of this group continues to belong to the group.” I think that’s a good and underappreciated point, but I also think it’s a bit weaker than it sounds at first, since something of a converse also holds. I.e. for permanent population decline to happen, we would only need a single human group satisfying the following two conditions: long-run below-replacement fertility, and a high enough “attraction rate”, that is, a large enough fraction of people born outside the group continue to join the group. “Western civilization” has arguably been such a group for the last few generations, and it’s not obvious to me that it (or its “descendants”) won’t continue to be for a very long time.
Thanks for writing this! For all the discussion that population growth/decline has gotten recently in EA(/-adjacent) circles, as a potential top cause area—to the point of PWI being founded and Elon Musk going on about it—there hasn’t been much in-depth assessment of the case for it, and I think this goes a fair way toward filling that gap.
One comment: you write that “[f]or a rebound [in population growth] to happen, we would only need a single human group satisfying the following two conditions: long-run above-replacement fertility, and a high enough “retention rate”, that is, a large enough fraction of the descendants of this group continues to belong to the group.” I think that’s a good and underappreciated point, but I also think it’s a bit weaker than it sounds at first, since something of a converse also holds. I.e. for permanent population decline to happen, we would only need a single human group satisfying the following two conditions: long-run below-replacement fertility, and a high enough “attraction rate”, that is, a large enough fraction of people born outside the group continue to join the group. “Western civilization” has arguably been such a group for the last few generations, and it’s not obvious to me that it (or its “descendants”) won’t continue to be for a very long time.