(Little bubbles, in the price of, say, individual stocks, happen all the time, and don’t qualify as an answer to the question.) And, because big bubbles last for many years, predicting them means predicting many years in the future, which is a bit like predicting who will be running the government two elections from now.
大规模的投机泡沫其实极少发生。（类似某只股票的股价这样的小型价格泡沫则是家常便饭，也不能作为问题的答案。）与此同时，由于大规模泡沫往往持续经年，预测它们就等于要预测未来数年内会发生何事，难度堪比预测两届大选过后的美国总统人选。