Canadian mining company Bre-X had soil samples from its Busang project examined for gold content in 1992. The positive news of gold being present attracted a range of investors - from unsophisticated individuals to saavy mining professionals - to invest in the Busang project. After years of successful promotion, the truth about this worthless property slowly emerged early in 1997 and drove Bre-X stock prices nearly to zero. A repeat analysis of the soil in 1997 indicated very low gold content. Thus the methods used to determine the gold content in 1992 must have been inaccurate.
Which of the following is an assumption on which the argument depends?