Tyler Cowen cites some recent research that answers the question, How many children should you have?:
In comparing identical twins, Kohler found that mothers with one child are about 20 percent happier than their childless counterparts; and while fathers’ happiness gains are smaller, men enjoy an almost 75 percent larger happiness boost from a firstborn son than from a firstborn daughter. The first child’s sex doesn’t matter to mothers, perhaps because women are better than men at enjoying the company of both girls and boys, Kohler speculates.Interestingly, second and third children don’t add to parents’ happiness at all. In fact, these additional children seem to make mothers less happy than mothers with only one child — though still happier than women with no children.