据美国社会学家詹姆斯·戴维斯（James C. Davies）的所谓的J曲线理论，革命 — — 如1917年俄国革命和1952年埃及革命 — — 发生在长期经济和社会发展被猛烈而突然地逆转的时期。
According to the American sociologist James C. Davies’s so-called J-curve theory, revolutions – such as the Russian Revolution of 1917 and Egypt’s revolution of 1952 – occur when periods of prolonged economic and social development are sharply and suddenly reversed.