Stock market bubbles occur when the prices of certain stocks or the overall market become significantly overvalued due to excessive speculation and investor euphoria.

Typically, a stock market bubble starts with a stark uptrend, where investors become more and more optimistic and euphoric regarding future performance, which creates an overpriced environment on the market. 

To briefly outline how stock market bubbles usually unfold, we can break it down into the following steps:

• Initial Uptrend: A bubble typically begins with a genuine increase in asset prices driven by positive news, economic factors, or innovation, attracting more investors
• Media and Public Attention: As prices rise, media coverage and public excitement increase. More investors enter the market, believing they can profit from the ongoing uptrend
• Excessive Buying: Investors' optimism leads to a frenzy of buying, pushing prices even higher, often detached from the underlying fundamentals
• Peak and Irrational Exuberance: Prices reach a peak fueled by "irrational exuberance," a term coined by economist Robert Shiller, which describes the unwarranted confidence in future price gains
• Correction or Crash: At some point, the bubble bursts, leading to a sudden and sharp decline in asset prices. Investors panic and rush to sell
• Losses and Damage: Many investors who bought near the peak suffer significant losses. The burst of the bubble can have economic consequences, such as job losses and financial instability
• Aftermath: After the bubble bursts, markets often stabilize and may eventually recover. Lessons are learned about the dangers of speculative bubbles

Common Reasons For Stock Market Bubbles

Some of the major reasons for stock market bubbles include the following:

• Excessive Speculation: Speculative buying, driven by the belief that prices will keep rising, can inflate asset values beyond their fundamentals
• Low Interest Rates: Low borrowing costs can encourage investors to take on more risk in search of higher returns, leading to asset price inflation
• Economic Booms: Periods of strong economic growth can create overconfidence and fuel speculation, pushing asset prices to unsustainable levels
• Herd Mentality: Investors often follow the crowd, leading to a self-reinforcing cycle of buying, even if it lacks a solid rationale
• Lack of Regulation: Weak or poorly enforced financial regulations can allow risky and speculative behavior to go unchecked

The Covid-19 Stock Market Bubble

A good example of a recent stock market bubble occurred during the Covid-19, when governments around the world enforced lockdown measures to combat the pandemic and spent billions of dollars in various stimulus programs to shield the economy from a major recession. 

Much of these stimulus funds found their way to the stock market, causing most equities to reach excessive valuations. 

If we look at the price chart of the S&P 500, we can see the 2020-2022 period as the boundaries of the Covid bubble, with a fast acceleration starting after a dramatic fall in March 2020, reaching the peak in 2021 and quickly dropping off in 2022. 

• A stock market bubble happens when the broader stock market is highly overvalued thanks to rampant speculation, low interest rates, or rapid economic growth
• Bubbles are typically accompanied by market corrections or crashes, which can destabilize the entire financial system 
• The Covid-19 stock bubble was the most recent example of an equity bubble that occurred between 2020 and 2022 
• Stock market bubbles can be caused by a wide range of factors, investor euphoria being one of the most common ones