Every parent I've ever known is glad that they had their last child. It doesn't matter how many children they've had, their last one was a good idea ex- post. One can turn that observation from anecdote to data by asking parents,
“taking everything into account, are you glad you had your last child?”
Presumably, the vast majority of them would say yes.
Ex-anti they oftentimes don't want to have one more, they will give all sorts of reasons for why having one more is not a good idea. But upon the actualization of such reasons, they almost never hold up, and they're glad they had their last one. One more baby is an investment that always yields a positive return.
Solutions?
1. Keep having one more baby
2. Taboo Bias. People fool themselves into thinking that their last child was a good idea because saying that Johnny shouldn't have existed is not nice.
3. What you see is all there is bias. People have trouble evaluating circumstances relative to the counter-factual. "I can't imagine life without my Johnny", if you can't imagine it, how do you know it's worse?
4. People are just really really good at deciding when not to have one more child. Almost everyone stops having babies exactly when one more baby is a bad idea.
