Here are the most important events that affected the cryptocurrency market in December over the years:

### 1. **Prices rise in 2017**

- **December 2017**: Bitcoin saw a massive surge to around $20,000. This surge was driven by increased interest from the media and individual investors.

### 2. **Launch Futures**

- **December 2017**: Bitcoin futures were launched on exchanges like CME and CBOE, bringing more legitimacy to the market and attracting institutional investors.

### 3. **Big Fluctuations in 2018**

- **December 2018**: After the huge rise in 2017, the market saw a major correction, with cryptocurrency prices falling sharply, leading to a market crash.

### 4. **Technical Developments**

- **Big Updates**: In December 2019, several major projects introduced important updates, such as Ethereum 2.0, which affected market sentiment.

### 5. **Institutional orientation**

- **December 2020**: The market saw the entry of a number of major institutions, such as MicroStrategy and Square, which helped drive prices up significantly.

### 6. **Global Organizations**

- **Regulation News**: In December 2020, several governments began discussing cryptocurrency regulations, raising investor concerns about future market impacts.

### 7. **Prices Rise in 2021**

- **December 2021**: Cryptocurrency prices saw new highs, with Bitcoin approaching $70,000, following a wave of investment interest.

### 8. **Market Events and Volatility**

- **Global Events**: Any major political or economic events, such as disease outbreaks or financial crises, could significantly impact market sentiment in December.

### a summary

December is often a crucial month for cryptocurrencies, with the market being influenced by a number of factors, from price increases to regulatory events. It’s important to keep up with news and analysis to better understand trends.