History of Coin Days Destroyed
The concept of Coin Days Destroyed (CDD) was introduced in a 2011 Bitcoin Forum thread by user “ByteCoin” as an alternative to transaction volume. The logic behind the proposal was that CDD was a more appropriate measure of the economic activity in Bitcoin.
Instead of measuring the transaction volume, which can be manipulated by one individual moving the same coins back and forth multiple times, CDD gives more weight to coins that have captured more time prior to being moved. For example, someone moving 1 BTC they received 300 days ago would hold just as much weight as someone moving 300 BTC they received one day ago.