To encourage or discourage population growth, different countries apply differents tax policies to ease the 'burden' of having children.
Luxembourg and Switzerland have the highest overall net income and the highest average gross wage. South Korea, Turkey and Poland families has almost no benefit, and Mexico has no benefits at all (Probably, because the average family has 2.4 children and Mexican government wants to cut it down) .
Click to enlarge. Source: Economist.com