There have been many major declines in the history of the cryptocurrency market. The following are several major declines and their backgrounds and impacts:

1. The Mentougou incident (February 2014): Mt.Gox, the world's largest Bitcoin exchange, suffered a hacker attack and lost nearly 850,000 Bitcoins, accounting for about 7% of the world's total Bitcoin. This incident caused the price of Bitcoin to plummet by 80%, triggering a crisis of confidence in the cryptocurrency market.

2. The September 4 incident (September 4, 2017): Seven ministries and commissions in mainland China jointly issued the "Announcement on Preventing the Risks of Token Issuance and Financing", defining ICO as an unauthorized illegal public financing behavior. After the announcement, Bitcoin fell 32% and Litecoin fell 57.3%. The entire cryptocurrency market fell into panic, and the market value evaporated by more than 80%.

3. The March 12 incident (March 12, 2020): Affected by the global epidemic and macroeconomic factors, the cryptocurrency market fell sharply, and a wave of liquidation swept in. Most assets fell by more than 40%, and investors suffered heavy losses.

4. ‌Luna Black Swan Event (2022): Terra's Anchor project offers an annualized rate of return of up to 20% on fixed deposits, attracting a large number of investors. However, due to the depegging of the algorithmic stablecoin UST, the price of Luna collapsed, resulting in huge losses in the market.

5. ‌FTX Explosion Event (2022): The collapse of the FTX exchange triggered a crisis of confidence in the entire cryptocurrency market. Although its impact was relatively small, it also highlighted the uncertainty of the market.

6. ‌5·19 Event (May 19, 2021): China's strengthened supervision of virtual currency speculation has led to market panic, and the prices of many currencies have fallen by more than 50%, especially Bitcoin, which has fallen by nearly 30% in a short period of time. The market explosion amount has reached 40 billion, involving as many as 480,000 people.

These events have not only affected the price of cryptocurrencies, but also had a profound impact on market confidence and the psychology of participants. When participating in the cryptocurrency market, investors should maintain a cautious and rational attitude, reasonably allocate assets, and avoid excessive losses due to market fluctuations.