Children are employed in many different types of jobs, and the employment relations governing their work vary accordingly. They may be wage labourers in factories or mines or self-employed workers engaged in street trades. Some are out-workers and others are seasonal migrant workers. Many are engaged in work that is the final link in a long chain of subcontracting. Some receive part of their wage in kind and some are paid on a piece-rate basis. Many are unpaid and work for their families in the home or on the land. Even if it is not itself" productive", children's work may release others for productive employment. Salazar shows that by performing domestic chores and taking care of younger children in the home, for instance, children free adults for wage labour, while Abdalla shows that child labour can facilitate adult migration to areas of high employment. Child employment may also be full time or part time. A high proportion of child workers attend school too and are therefore recorded in official statistics as pupils and not as labourers. Most child workers are found in unregistered and undercapitalised enterprises operating in a competitive and often highly volatile or seasonal market. These face stiff competition from larger, more mechanised companies and are forced to sell their products in a depressed market. In such circumstances it is more advantageous to employ children than adults: they can be easily laid off when business is slack; they cost less; and they have no rights as workers and cannot join trade unions. Child labour then is, more often than not, casual labour. The Institute of Industrial Relations (IIR) of the University of the Philippines found that virtually all establishments employing children in the wood and garment industries were small and unregistered, using a casual labour force paid on a piece-rate basis. Abdalla shows that children in the leather-tanning industry in Cairo constitute the most transient element in the labour force. The