This fourth issue of the Yearbook ‘Kondratieff Waves’ has the subtitle ‘The Spectrum of Opinions’, as its papers cover a whole range of problems. The Yearbook consists of three sections. The Introduction of this issue is dedicated to Nikolai Kondratieff's ideas which still are important to an analysis of the world economic situation. The first section (Long Waves in the Context of World Economy and Politics) includes five contributions devoted to the study of different spheres from economy to jihadism. The speeches of Kondratieff medal laureates are published in the second section (Kondratieff Medal: Winners' Speeches). It presents a very impressive collection of different views of well-known and young researchers. The last section (Reviews and Notes) includes Antony Harper's review of Leonid Grinin, Andrey Korotayev and Arno Tausch's monograph ‘Economic Cycles, Crises, and the Global Periphery’ published by Springer International Publishing. This issue will be useful for economists, social scientists, as well as for a wide range of those interested in the problems of the past, present, and future of global economy and globalization.