The price of a single bitcoin, which reached as high as $20,000 on some exchanges yesterday, retreated into correction territory today.

At 14:30 UTC, the price of a single bitcoin was $15,435, down 8.4 percent in the last 24 hours on the Coindesk index. Mirroring the decline in bitcoin’s price is a decrease in its average block reward and increase in fee percentage of the total block reward.

Other cryptocurrencies gained steam from bitcoin’s fall. As of this writing, six of the top 10 world’s most-traded cryptocurrencies were up. IOTA, a cryptocurrency designed for Internet of Things (IoT) transactions, was the biggest gainer, soaring 12 percent within the last 24 hours. It has registered average daily growth in double digits in the last week, except for a blip yesterday. (See more: A Closer Look at IOTA.)

Bitcoin rival Bitcoin Cash also rose by 8 percent while Ripple was up by 9 percent. On an overall basis, the cryptocurrency market was worth $418 billion, down from yesterday’s high of $426.7 billion. 

Can Bitcoin Whales Manipulate Bitcoin Prices?

Recent volatility in bitcoin prices has mostly been attributed to investor enthusiasm for introduction of bitcoin futures trading at CME and CBOE. The last 12 hours seem to have tamped down that enthusiasm. (See more: What Was Behind Bitcoin’s Insane Price Moves On Dec. 7?)

Now a Bloomberg news item posits that bitcoin whales, or people who own 40 percent of total bitcoins in circulation, might be behind its price swings. Bloomberg quotes traders and analysts who estimate that there are between a “few hundred” to 1,000 such users. What’s more, the top 100 bitcoin addresses control 17.3 percent of all bitcoins in circulation. (See also: Winklevoss Twins Are Bitcoin's First Billionaires.) 

These investors use a variety of tactics to control bitcoin’s price. For example, they might institute large future orders at a certain price level that benefits their holdings. Because there are a limited number of bitcoins in circulation and bitcoin whales own a substantial quantity, they can force price movements in the market. (See also: Why Do Cryptocurrencies Have Buy And Sell Walls?)

Collusion is necessary to ensure this. According to the Bloomberg article, bitcoin whales might be in touch with each other. There are no legal barriers to prevent them because bitcoin is a digital currency and not a security. “There’s no prohibition against a trade in which a group agrees to buy enough to push the price up and then cashes out in minutes,” said Gary Ross, a securities lawyer.