Orders placed by specialists are likely to be influenced by manufacturers' sales representatives or by anecdote and hearsay rather than by systematic study of all available products conforming to a defined specification or need, made by a competent supplies officer with some knowledge of the relevant products available on the market. There is evidence that the majority of orders placed by other than supplies staff are for goods on contracts convened by the supplies department and approved by the supplies department and for manufacturers who have been approved and vetted by the supplies department. DHSS insists on having several suppliers in order to safeguard deliveries and to avoid the creation of monopolies. DHSS needs accurate retrospective computerised accounts of supplies received in each region for each commodity, giving the price and name of the manufacturer. One of the most common grievances among suppliers is the absence of any certainty about the quantity of goods that will be in fact purchased.