Vertical integration describes a style of management control. Vertically integrated companies are united through a hierarchy with a common owner. Usually each member of the hierarchy produces a different product or service, and the products combine to satisfy a common need. It is contrasted with horizontal integration. Vertical integration is one method of avoiding the hold-up problem. A monopoly produced through vertical integration is called a vertical monopoly, although it might be more appropriate to speak of this as some form of cartel. Andrew Carnegie actually introduced the idea of vertical integration. This led other businessmen to using the system to promote better financial growth and efficiency in their companies and businesses.