Peter Drucker is considered the "Godfather of Management" for coining terms like "knowledge worker." He believed people are an organization's most valuable asset and that there is no business without customers. Drucker identified six functions of management including planning, organizing, staffing, leading, controlling, and motivating. The evolution of management in the US has been influenced by wars, technology, the Industrial Revolution, and the rise of knowledge workers. In the late 1990s, a "Silent Revolution" changed the business environment across five fronts including the flow of information, global reach, demographics, empowered customers, and dissolving industry walls.