Factors that don't correlate much with happiness include: age,7 gender,8 parenthood,9 intelligence,10 physical attractiveness,11 and money12 (as long as you're above the poverty line). Factors that correlate moderately with happiness include: health,13 social activity,14 and religiosity.15 Factors that correlate strongly with happiness include: genetics,16 love and relationship satisfaction,17 and work satisfaction.18

This is not the sort of thing you can give "an answer" to. Other studies have found that age, intelligence, attractiveness, and money correlate well with happiness. A recent study found that money correlates with happiness up to $75,000/yr, which I would not call poverty. Health, wealth, and happiness all correlate so strongly that picking one out as causal is difficult. And other studies have found that parenthood correlates negatively with happiness while your children are living at home; I expect it corresponds positively once they've moved out.