What binds Rick Warren, Tyler Cowen (and Megan McArdle)

this reminded me of this:

I can see a few theories of our duties:

a. Do that which yields the highest net social return if only you do it.

b. Do that which yields the highest net social return if many people were to do it.

c. Cut back on your activities which most closely resemble aggressive interference into the lives of others.

d. Perform the action most likely to influence the behavior of others.

Belief in "a" favors sending money. Belief in "b" favors having fewer children. Belief in "c" favors restricting your driving and flying. I am not sure which course of action follows from belief in "d."

I did challenge the good professor Cowen on .b., though, with this comment:

I believe that a child:

+ costs about $200,000 to raise
+ creates about $2 million in value
+ pays about $600,000 in taxes

Given these assumptions and doing the math, it appears that having more children is the correct answer.