"There is nothing intrinsic to parenthood that makes people less happy—and nothing intrinsic to parenthood that makes people any happier, for that matter."

"In some countries, most notably Norway and Hungary, parents are actually happier than non-parents."

The fact that having children makes people unhappy only tells a truth about societies being wrongly structured, rather than anything about the happiness of having children.

That's also from a strictly American perspective where having children is much different in aggregate than other societies. If you look at LDS communities they tend to be a pretty happy group while having much larger families than the average US household.