Young coins are usually classify as coins which have transacted in the last 3-to-6 months. This supply is unlikely to be lost, and is actively participating in the day-to-day trade of the Bitcoin economy.
The chart shows the following traces:
Younger coins can be seen to typically swell in volume during two key events:
Bull markets as longer-term investors spend and divest into market strength.
Capitulation sell-off events where widespread panic brings coins of all ages back into liquid circulating.
A significant increase in young coin volumes indicates more supply is actively transacting within the on-chain economy, and may lead to an overwhelming of demand. Conversely, long periods of accumulation result in more coins taken into cold storage, reducing supply immediately available on the market.