Bitcoin fell below $6,000 for the second time in a week Friday, June 29, the day CME Group’s Bitcoin futures end their last day of trading for the month.

Data from Cointelegraph’s price index and Coin360.io show Bitcoin continuing a trend of declines in the run-up to futures expiration dates.

At press time Friday, BTC/USD is trading around $5,850, down 4.4 percent on the day, while signalling monthly losses of over 20 percent.

Major altcoins had followed suit, Ethereum (ETH) down 5.6 percent to $412 and Ripple (XRP) 6.5 percent to just under $0.43 per coin.

Market visualization from Coin360

Together with a brief period in early February when BTC’s price neared $6K, this week’s sub-$6,000 Bitcoin prices – the last one before today occuring Sunday, June 24 – mark the third occasion that the price barrier has been breached in 2018.

The effect of futures trading periods on Bitcoin has meanwhile become an increasingly convincing metric for measuring market sentiment.

Earlier this month, Fundstrat Global Advisors’ Tom Lee, known for his bullish stance on Bitcoin’s future price, argued that similar deadlines for CBOE’s futures had suppressed price growth.

In May, the Federal Reserve Bank of San Francisco released an Economic Letter suggesting that Bitcoin’s decline since its $20,000 peak in December was the result of the launch of Bitcoin futures trading.

Social media commentators identified further trends, suspecting banks’ involvement in futures as the main culprit behind Bitcoin’s failure to grow higher. CME trading Uranium futures produced similar behavior in the sector, one Twitter user noted.

More broadly, however, sources remain at odds over Bitcoin prices. Research data published this week dispelled concerns markets were subject to manipulation, instead concluding investors were buying and sitting on their coins.