> I think that to raise a child can be
 > considered in economics a
 > "merit good" (private good with positive externality)
 > Luigino Bruni


As stated by Nicolaus Tideman, "Whether added births represent a net 
gain or net loss when the value of exclusive access to Nature is 
shared is not 
clear."  http://www.usbig.net/papers/084-Tidemand-Ehtics-o-BIG.doc

One more child can have both positive and negative externalities.

A greater population increases congestion and depletes more natural 
resources.  It is also uncertain whether a particular child will 
become a criminal or have costs such as high medical expenses.

Thus in my judgment, the least arbitrary a priori proposition 
regarding the costs and benefits of another child is neutrality.

Fred Foldvary