Researchers wondering why having children doesn’t tend to make people happier have found one leading factor — financial stress. A family earning an average salary spends about $250,000 per child from birth through age 17, according to U.S. federal government data. Without the costs of raising a child factored in, the presence of children brings parents happiness, two economists found. The happiest parents tend to be those below the age of 45 who are living with a partner.