Around 4 million btc have been lost forever due to losing private keys or long term hodling or maybe even due to transaction fees. This implies that 1/4th of total mined supply is lost which implies the reason why bitcoins price is really booming a lot. According to new research from Chainalysis, a digital forensics firm that studies the bitcoin blockchain, 3.79 million bitcoins are already gone for good based on a high estimate—and 2.78 million based on a low one. Those numbers imply 17% to 23% of existing bitcoins, which are today worth around $8,500 each, are lost.