The Peercoin network activated in 2012 and is one of the first cryptocurrencies to ever be released. It is responsible for inventing proof-of-stake consensus, which makes it the first efficient and sustainable public blockchain technology. Peercoin was inspired by bitcoin, and it shares much of the source code and technical implementation of bitcoin. The Peercoin source code is distributed under the MIT/X11 software license. Unlike bitcoin, Namecoin, and Litecoin, Peercoin does not have a hard limit on the number of possible coins, but is designed to eventually attain an annual inflation rate of 1%. There is a deflationary aspect to Peercoin as the transaction fee of 0.01 PPC/kb paid to the network is destroyed. This feature, along with increased energy efficiency, aim to allow for greater long-term scalability.