Coins have a birthday
Bitcoin’s ledger is built from unspent transaction outputs, or UTXOs. Each is a chunk of coin that was created by some earlier transaction and has not yet been spent. Every UTXO therefore has an age: the time since the transaction that created it was confirmed. When it is spent, it disappears and new outputs are created, which start again at age zero.
This is a particularly handy feature for analysis. Without knowing who owns anything, you can see how long each chunk of coin has sat still.
Grouping into age bands
Looking at millions of individual outputs is impractical, so providers sort them into bands by age, for example less than one day, one day to one week, one week to one month, then one to three months, three to six months, six to twelve months, and so on out to several years. The exact band edges differ between providers.
Two common ways to show the result are:
- Supply by age band. For each band, the number of coins whose last movement falls in it, shown over time. Stacked charts, sometimes called “wave” charts, make shifts easy to see.
- A single cutoff. Many dashboards split supply at roughly 155 days or at one year, labelling the younger group “short-term holders” and the older group “long-term holders”. The cutoff is a convention chosen by analysts, not a feature of the protocol.
A checked example
Suppose an imaginary network has 100 coins in total, split like this:
| Age band | Coins |
|---|---|
| Under 1 month | 10 |
| 1 to 6 months | 20 |
| 6 to 12 months | 15 |
| Over 1 year | 55 |
The shares are 10%, 20%, 15% and 55%, which sum to 100%. With a one-year cutoff, 55% of supply would be labelled long-term and 45% short-term.
Now suppose a holder moves 5 coins from the “over 1 year” band into a new wallet. They drop to age zero. The over-one-year band falls to 50 coins (50%) and the under-one-month band rises to 15 (15%). Nothing was sold, but the chart shows a shift toward younger coins. That small example captures the main interpretive difficulty.
How the bands are usually read
The standard reading is behavioural. Coins that have been still for a long time are presumed to belong to holders who are not trading, while young coins belong to more active participants. A growing share of old coins is read as accumulation or holding conviction, and old coins moving again is read as long-term holders spending or selling.
Analysts also watch the age at which coins are spent. When very old coins suddenly move, it draws attention, partly because it breaks a long period of inactivity. It might reflect a sale, an inheritance, a security upgrade or the revival of a forgotten wallet.
Why the reading is shaky
Moving is not selling. Any transfer resets the age, including moves between a person’s own wallets, wallet migrations and custody changes. A holder who upgrades to a new hardware wallet and sweeps their coins appears to have “spent” old coins.
Selling is not always visible. Coins sold inside an exchange account, or traded through a custodian, do not move on the chain. They stay in an old band while ownership changes. Exchange wallets in particular hold customers’ coins, and their ages reflect the custodian’s operations, not individual customers’ behaviour.
Old coins include lost coins. Some of the oldest bands contain coins whose keys have been lost, as discussed in the article on lost coins. These coins can never move, so a rising old-coin share partly reflects accumulating dead supply and not only deliberate holding.
Labels are stereotypes. “Long-term holder” simply means a coin that has not moved for the cutoff period. It does not identify a type of person. A trader might leave coins untouched for a year, while an investor might shuffle them monthly.
Ageing is mechanical. In a period with little movement, coins automatically migrate into older bands as time passes, so the old-coin share rises even without any deliberate decisions. Interpreting such drifts as conviction can be a mistake.
Entity effects. Large institutions, ETF custodians and exchanges can hold or consolidate enormous amounts, and a single decision moves a visible share of supply. The pattern may say more about a few entities than about typical holders.
Using age data sensibly
Age bands are best seen as a descriptive picture of how recently coins have been in motion. They pair naturally with realized cap, which weights coins by the price when they last moved, and with the study of whale wallets. Compare changes over months, not days, and test any story against alternative explanations such as custody moves.
Cryptocurrency prices are volatile, patterns in coin age have no proven power to forecast them, and people can lose everything they invest. Nothing here is financial advice.