However, by using a data collection method that differentiated between addresses belonging to intermediaries and individuals, NBER researchers were able to find that the former controlled about 5.5 million Bitcoin at the end of last year, while the latter controlled about 8.5 million.
Such a high concentration could make the Bitcoin network vulnerable to a 51 per cent attack, where a colluding set of miners or one miner is able to take control of a majority of the network.