From Longman Dictionary of Contemporary Englishthe pendulumthe pendulumCHANGE/BECOME DIFFERENTused to talk about the tendency of ideas, beliefs etc to change regularly to the opposite After several years of Republican government, the pendulum will undoubtedly swing back and voters will elect a Democrat.the pendulum of the pendulum of fashion → pendulum
Examples from the Corpus
the pendulum• Highly paid banking jobs were seen as very desirable in the 1980s, but the pendulum is swinging the other way now.• Today, the fashion pendulum is swinging back to casual clothes. 