Peercoin

Peercoin, also known as PP Coin or PPC, is a peer-to-peer cryptocurrency utilizing both proof-of-stake and proof-of-work systems.

Peercoin is based on an August 2012 paper which listed the authors as Scott Nadal and Sunny King. King, who also created Primecoin, is a pseudonym. Peercoin is the first implementation of a proof-of-stake based Cryptocurrency. The Peercoin source code is distributed under the MIT/X11 software license.

In the proof-of-stake system, new coins are generated based on the holdings of individuals. In other words, someone holding 1% of the currency will generate 1% of all proof-of-stake coin blocks. This has the effect of making a monopoly more costly, and separates the risk of a monopoly from proof-of-work mining shares.

Economics
Proof-of-work and proof-of-stake both serve as means of distributing new coins.

A transaction fee prevents spam and is burned (instead of being collected by a miner), benefiting the overall network.

To recover from lost coins and to discourage hoarding, the currency supply targets growth at 1% per year in the long run.