Apparent trends in stock prices may be pure statistical illusion

Evidence

If it were indeed the case that “what looks like a purposive movement over a long period” in an economic time series was “merely a kind of economic Brownian motion,” then any “trends or cycles” apparently observed in such series would be “illusory” (ibid., pp. 13, 18). — Donald MacKenzie, An Engine, Not a Camera, 274

Categorization

• DEFINE: This is the seeds of the random-walk idea that the whole performativity thesis circles around.
• XREF: Links to the financial economics random-walk literature that Samuelson formalizes later in this book.