Assets that grind higher over decades rarely reverse course suddenly. Instead, the prolonged, slow uptrend builds investor complacency, leading to an overbought state and a final parabolic surge. This blow-off top is the necessary precondition for a significant, sustained decline, a pattern Gurevich notes he missed in the bond market.

A key warning sign of a market top is low correlation, where different indices (e.g., NASDAQ, S&P 500, Russell 2000) peak at separate times. This indicates that capital is rotating from exhausted leaders to laggards in a final, desperate search for returns. When this rotation ends, the next likely move is a broad, correlated decline.

A true bubble, like the dot-com crash, involves stock prices falling over 50% and staying depressed for years, with capital infusion dropping similarly. Short-term market corrections don't meet this historical definition. The current AI boom, despite frothiness, doesn't exhibit these signs yet.

Historical data shows no exceptions to the rule that an asset class reaching a two-standard-deviation (two sigma) valuation above its long-term trend will eventually return to that trend. This statistical certainty applies to stocks, bonds, commodities, and currencies, making severe drawdowns from such peaks inevitable.

Calling a market top is a technical exercise, as fundamentals lag significantly. A reliable sell signal emerges when the market's leadership narrows to a few "generals." When a critical number of these leaders (e.g., three of the top seven) fall below their 200-day moving average, the rally is likely over.

A rare but reliable historical indicator of a market peak is when speculative, high-flying stocks begin to decline even as the broader blue-chip market continues to climb. This divergence, seen in 1929, 1972, 2000, and 2021, signals a late-stage rotation to perceived safety just before a major downturn.

A key indicator of a bubble's final stage, observed only four times in U.S. history (1929, 1972, 2000, 2021), is when speculative, high-beta stocks that led the rally start to fall sharply while blue-chip indices continue to grind higher. This market divergence is a 'primal scream' that a crash is imminent.

A market enters a bubble when its price, in real terms, exceeds its long-term trend by two standard deviations. Historically, this signals a period of further gains, but these "in-bubble" profits are almost always given back in the subsequent crash, making it a predictable trap.

Contrary to intuition, widespread fear and discussion of a market bubble often precede a final, insane surge upward. The real crash tends to happen later, when the consensus shifts to believing in a 'new economic model.' This highlights a key psychological dynamic of market cycles where peak anxiety doesn't signal an immediate top.