It is known that when people generate externalities, a birth also generates an externality and efficiency requires a Pigou tax/subsidy on having children. The size of the externality from a birth is important for studying policy. We calculate the size of this "population externality" in a...

We calculate the harm a birth imposes on others when greenhouse gas emissions are a problem and a cap limits emissions damage. This negative population externality, which equals the corrective Pigovian tax on having a child, is substantial in calibrations. In our base case, the Pigovian tax is...

Democracies around the world are making promises to the old at the expense of future generations. I interpret this as reflecting low altruism—a discount rate on children’s utility greater than the world interest rate—and I examine the implications in a small open economy with overlapping...