1980s, and Microsoft then moved ahead with its own market-dominating Windows system. By 1999, IBM also agreed to develop new computer technologies jointly with Dell Computer, a strong new entry into that market. Just as the merger wave of the 1960s and 1970s led to series of corporate reorganizations and divestitures, the most recent round of mergers also was accompanied by corporate efforts to restructure their operations. Indeed, heightened global competition led American companies to launch major efforts to become leaner and more efficient. Many companies dropped product lines they deemed unpromising, spun off subsidiaries or other units, and consolidated or closed numerous factories, warehouses, and retail outlets. In the midst of this downsizing wave, many companies -- including such giants as Boeing, AT&T, and General Motors -- released numerous managers and lower-level employees.