What it means
A broad market can fall substantially even when some individual stocks rise. A bear market describes an extended downturn, usually measured using a stock market index rather than the price of one company’s shares. A decline of at least 20% from a recent peak is a common convention, not an official rule that every market follows.
The chosen index matters: a national index, a regional index and a sector index may reach that threshold at different times. A bear market is not the same as a recession, which concerns economic activity. Nor does the label establish why prices fell or when the decline will end.
How it is calculated
To test the common 20% threshold, compare an index level with its earlier peak:
Decline (%) = (Peak index level − Current index level) / Peak index level × 100
- Peak index level is the index’s earlier high over the period being examined, measured in index points.
- Current index level is its level at the observation time, also in index points.
- Decline (%) is the percentage decrease from that peak. The index-point units cancel in the division.
Under the common convention, a decline of 20% or more meets the numerical threshold. Analysts may differ on which peak to use, whether to compare closing levels or intraday levels, and how long a decline must persist. State those choices when comparing bear-market dates.
Worked example
Suppose a hypothetical broad stock index reaches a closing peak of 5,000 points. Later, its closing level is 4,000 points.
- Subtract the current level from the peak: 5,000 − 4,000 = 1,000 points.
- Divide by the peak: 1,000 / 5,000 = 0.20.
- Convert to a percentage: 0.20 × 100 = 20%.
The index has reached the commonly used bear-market threshold on this closing-level measure. If it were at 4,100 points instead, the decline would be 900 / 5,000 × 100 = 18%—below that threshold. Neither calculation says what happens next or how any particular stock will perform.
Why it matters before you trade
A bear-market label gives context, but an index-level decline cannot substitute for checking a proposed stock trade. Individual stocks can have different liquidity, volatility and news exposure from the index. Order size also matters: an order that represents a large share of a stock’s daily trading volume may face different execution conditions from a smaller one.
Before placing an order, a pre-trade check can examine the stock’s estimated bid-ask spread, the order’s participation in daily volume, potential market impact and the basket’s concentration. These measures address risks and costs that the 20% index threshold does not measure. They are estimates, not assurances about a fill price or an investment outcome.
How PreTrAIde uses it
The product facts do not identify a bear-market classification or a 20% index-decline test as a PreTrAIde input or output. PreTrAIde provides pre-trade analysis for a user-built stock basket before the user places any order. Its quantitative layer estimates measures including spread, daily volatility, market impact, participation in daily volume and one-day 95% value at risk.
PreTrAIde returns a GO, NO-GO or MODIFY verdict for the basket and each line, with a model-estimated success probability, risk assessment, suggested execution strategy and plain-language reasoning. Those verdicts support a decision; they are not recommendations or guarantees. PreTrAIde does not place orders.
Common mistakes
- Treating 20% as a universal rule. It is a widely used convention; measurement choices can change the date a threshold is reached.
- Calling one falling stock a bear market. The term normally refers to a broader market or specified index.
- Equating an index decline with every stock’s risk. Stock-level volatility, liquidity and execution costs can differ substantially.
- Assuming the label predicts the next move. A decline measured from past index levels cannot determine future prices.