Socionomics: How Social Mood Shapes Society explores the main principles and applications of socionomic theory as elaborated by Robert Prechter. Socionomic theory posits that an omnipresent social mood, shifting constantly in a wave form through all aspects of society, is responsible for the aggregate tenor and character of all social, economic and cultural trends, from fluctuations in the stock market to the popularity of particular genres of music at a given time. The social mood as an endogenous and collective force has its roots in the herding instinct often identified amongst crowds. Individuals typically make rational decisions when acting alone, and in the context of certainty, but in groups and in context of uncertainty, mood-based mimetic behavior can affect all the participants. As social mood often goes unnoticed, people tend to give their collective feelings labels to rationalize them, thus constituting ‘public opinion’. Therefore, whilst ‘public opinion’ as presented in the media is usually seen as rational, it is in fact based on the social mood context that often determines how people think, feel and behave. As the internet and social media have become ubiquitous in our daily lives, these rationalizations are spreading faster and faster than ever before and creating a pseudo-reality which can corrupt the collective perception of what is real and what is not. This stimulating and thought-provoking book will be of great interest to academics, practitioners and policymakers with an interest in the humanities and social sciences, particularly sociology and economics. © 2024 Mikko Ketovuori.