Key points:Bitcoin has seen its largest 30-day illiquid supply increase of the current bull market.Illiquid supply now stands at 14 million BTC, more than ever before.Whales are still accumulating as the price returns to six figures.Bitcoin (BTC) investors are turning the BTC supply more illiquid than at any point in its historyData from onchain analytics platform Glassnode shows that Bitcoin’s “illiquid supply” has reached a record 14 million BTC.Bitcoin illiquid supply returns to all-time highsBitcoin is increasingly finding its way into the hands of entities that do not sell what they acquire.Glassnode, which charts the portion of the BTC supply owned by so-called “illiquid entities,” reveals that this has reached levels not seen during the current bull market.An entity is considered illiquid if the ratio between its cumulative BTC inflows and outflows is below a certain value.“This ratio yields a number L between zero and one, with larger values indicating higher liquidity,” it explained in a dedicated guide.“Liquidity is therefore the extent to which an entity spends the assets it receives. Illiquid entities are those that hoard coins in anticipation of a long-term BTC price appreciation.”Bitcoin illiquid supply. Source: GlassnodeIlliquid supply stood at just over 14 million BTC this week, with the 30-day rolling increase coming in at 180,000 BTC, its largest jump since December 2022.At the time, the previous bear market was coming to an end, with BTC/USD declining 77% to hit long-term lows of just above $15,000 in the process.Bitcoin 30-day illiquid supply change. Source: GlassnodeWhale BTC accumulation “significant”As Cointelegraph continues to report, this bull cycle stands out in terms of investment trends thanks to increasing institutional participation.Related: BTC bulls get ‘biggest signal’ — 5 things to know in Bitcoin this weekCorporate treasuries, such as that of business intelligence firm Strategy, have combined with the US spot Bitcoin exchange-traded funds (ETFs) to make Bitcoin a mainstream investment target.Onchain data likewise shows that Bitcoin whales have accumulated throughout the recent BTC price rebound. Only retail investors appear to be panicking.“Bitcoin’s key whale & shark tier (holding 10-10K BTC) have now accumulated 83,105 more BTC in the past 30 days,” research firm Santiment reported in an X post this week. “Meanwhile, the smallest retail holders (holding Bitcoin whale and shark accumulation data. Source: Santiment/XThis article does not contain investment advice or recommendations. Every investment and trading move involves risk, and readers should conduct their own research when making a decision.