International aid can come in the form of short-term emergency aid for natural disasters or wars, providing food, clothing, medicine and shelter. Long-term aid helps countries develop over months or years through infrastructure projects like hospitals, schools, power stations and roads. Official aid comes from other countries or groups like the UN using tax money, while voluntary aid comes from charitable donations. Countries provide aid to help poorer countries develop so they can trade more, and to gain political support, while some see it as a moral duty. However, aid is not always effective and can cause problems if unsuitable, does not reach the needy, or creates other issues. Small-scale self-help schemes that involve local people and technology may be