How do circuit breakers protect investors?

In electronics, a circuit breaker is a safety device designed to prevent damage by interrupting the flow of electricity whenever there's an overload. It trips to break the circuit and protect the system from harm.

Similarly, circuit breakers in stock markets act as automatic trading halts triggered when there's excessive buying or selling activity. If the market moves beyond a certain threshold - whether sharply up or down - trading is temporarily paused or even halted for the day.

While these two types of circuit breakers operate differently, they share a common goal: protecting the system. In the market, circuit breakers help shield investors from drastic losses by curbing panic-driven selling and extreme volatility within a single trading day.

In this article, we'll explore how these mechanisms work, their benefits, and their limitations.

What are circuit breakers in the stock market?

Circuit breakers are automatic trading halts that kick in when prices of stocks or stock indices rise or fall beyond certain predefined thresholds within a trading day. The primary goal is to temper extreme volatility and give market participants time to reassess market conditions, preventing knee-jerk reactions.

The concept was introduced globally after the Black Monday crash in 1987, where the Dow Jones Industrial Average fell more than 20 per cent in a single day. Since then, circuit breakers have become standard features in stock markets worldwide, including India's National Stock Exchange (NSE) and Bombay Stock Exchange (BSE).

However, as mentioned, there's an upper circuit too. For instance, trading was halted back in 2009 when Indian markets had a sharp rally of 10 per cent during a single trading day.

Suggested read: Mechanical rules for investing

How do circuit breakers work?

Circuit breakers function at two levels: for individual stocks and for entire stock indices such as Nifty 50 or Sensex. When price movements cross certain percentage thresholds, trading is temporarily paused for a predetermined time.

For instance, here's the protocol followed for NSE:

The period during which trading gets halted is known as a cool-off period - it helps calm panic in the market.

Here's a notable instance of circuit breakers dampening the impact of a falling market. On 23rd March, 2020, right before a nationwide lockdown was imposed, the Sensex fell by close to 4000 points. Naturally, circuit breakers were instituted. This measure was taken to curb panic in the market.

That said, there are some limitations to this system.

Suggested read: Stick to the basics

What are the limitations and challenges of circuit breakers?

Here's what critics of circuit breakers say:

• The magnet effect: As the market falls, nearing the point where a circuit breaker will get triggered, more people begin panicking. After all, the window for selling stocks will close soon. As a result, more people begin selling, leading the circuit breaker to set off quicker.
  
• Interrupts proper price discovery: Critics argue that instead of curbing the volatility inherent in stocks, it prolongs it. For instance, if a stock is falling due to some negative press and hits the lower circuit, and continues falling the next day as well. It is unable to reach its intended low price within the same day.
  
• Contagion paradox: This argument suggests that if a stock belonging to a certain index spirals downwards, it can bring the entire index to fall. And if the fall is significant enough to show up as a decline on the index, investors may panic. As a result, this can cause anxiety in the market as a whole.

Conclusion

Circuit breakers are crucial safeguards in stock markets, designed to prevent panic-driven crashes and maintain orderly trading. Understanding how these mechanisms work and what to expect during trading halts can empower investors to stay calm and make rational decisions.

Instead of reacting impulsively when circuit breakers trigger, investors should use the pause to reassess their portfolios and stick to long-term strategies. As markets evolve, circuit breakers will continue to play a vital role in preserving investor confidence and market stability.

As we discussed in our previous article , if fear grips the market, you should use that moment to take an opportunistic call.

Also read: Understand and control

This article was originally published on May 22, 2025.