The global advertising industry has experienced major consolidation, with a few large communication companies controlling most major advertising, public relations, research, and digital marketing services. Visit the websites of the communications groups WPP, Omnicom Group, Interpublic Group, and Saatchi & Saatchi. Based on the information provided about these companies, create a list of factors that global marketers should consider when working with the agencies to create a global advertising campaign and provide advertising services in major countries. Discuss your reasoning.