From Vox (not the Vox you're thinking of, but another Vox), an article on why it's so complicated to analyze the impact of having children on one's happiness.

It is a commonplace that new parents are overwhelmed by a “tsunami of love” when they first meet their dependent offspring. Older children, though often a source of irritation and worry, are also a source of joy, and there are few parents who can even bear to think of a world without their children. Yet, study after study has shown that those who live with children are less satisfied with their lives than those who do not; Hansen (2012) and Stanca (2012) are recent surveys. How can this be? Should governments publicise such findings, to help disabuse people of the widespread notion that children are good for them? Perhaps along with Larkin’s lines?
Is there something wrong with these empirical analyses? Or is it that, as many economists suspect, happiness measures are unreliable? We argue here that the results are correct, as far as they go. The deeper problem is that comparisons of the wellbeing of parents and non-parents are of no help at all for people trying to decide whether or not to become parents.

Worth reading the rest for the complexities of structuring a study to tease out the answers everyone is seeking on this question.