 Operations managements principles of variability reduction and management are applied by buffering through a combination of capacity, time and inventory.Service industries are a major part of economic activity and employment in all industrialized countries comprising 80 percent of employment and GDP in the U.S. Operations management of these services, as distinct from manufacturing, has been developing since the 1970s through publication of unique practices and academic research.Please note that this section does not particularly include "Professional Services Firms" and the professional services practiced from this expertise (specialized training and education within).