Proof of Importance

''Proof of Importance

The detailed overview can be found in NEM’s Technical Reference document. In general, it looks like a variation of Proof of Stake that gives extra weight to accounts that are actively transacting with a lot of other accounts. The actual equations as to how the weight is calculated and how it affects who will be selected as a miner is detailed over several pages of the document.’’ The Piachu’s Bitcoin Blog Post