Children are often forced to work due to chronic poverty. Globally, work is the main occupation of almost 20 percent of all children aged under 15. This is considered a major obstacle to achieving the Millennium Development Goal (MDG) of universal primary education by 2015. Research from the University of Oxford in the UK suggests that child labour is often essential to household survival. Children who do household work release adults from domestic responsibilities to earn a wage; those employed outside the home contribute to family income.