The tumble taken by investor sentiment across the asset class spectrum in recent weeks has triggered some of the sharpest price falls in years. Copper is no exception, where sentiment has suffered its largest one-week fall in five years, according to an exclusive index of trader views in three key markets - Shanghai, New York and London - by brokerage Marex Spectron. The 30.1-point fall on the index takes it down to minus 34.9, its lowest reading since April. Marex Spectron's head of market analytics, Guy Wolf, thinks the worst is yet to come. "Sentiment extremes have tended to occur on the pessimistic side in recent years so past experience would suggest we have not yet seen the lows."