N-SING
（局勢意見等的）搖擺不定，變化不定
You can use the idea of a pendulum and the way it swings regularly as a way of talking about regular changes in a situation or in people's opinions.
例句
The pendulum has swung back and the American car companies have made dramatic advances in safety...
三十年河東，三十年河西，美國汽車公司在安全方面已經取得了巨大進步。
The political pendulum has swung in favour of the liberals.
政治形勢轉而對自由主義者有利。