Coin Days and Dormancy
Understand coin days destroyed, dormancy, age-weighted spending and why old-coin movement is context rather than an automatic bearish signal.
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Coin-day metrics weight on-chain spending by the age of the coins involved, helping distinguish movement of long-dormant supply from routine turnover.
What it measures
A coin day is generated when one coin remains unspent for one day. If 10 coins sit for 30 days, they accumulate 300 coin days. When those coins are spent, the accumulated age is considered “destroyed”.
Coin Days Destroyed (CDD) therefore gives older supply more weight than recently moved supply. Dormancy relates age-weighted destruction to transaction or spent volume, helping characterise the average age of coins moving.
How the metric works
A 1 BTC output held for 1,000 days contributes 1,000 coin days when spent. A 100 BTC output held for only one day contributes 100 coin days. This weighting makes movement of old supply visible even when transaction count or coin quantity is small.
Dormancy normalises age-weighted activity by the amount of supply moving, though provider formulas can vary. A high dormancy reading generally means older coins are contributing more heavily to current spending than usual.
UTXO consolidation is an important confounder. A holder can reorganise many old outputs into a new wallet, destroying years of coin days without changing beneficial ownership. Custodians can do the same during wallet migrations.
Age-weighting can also make tiny ancient outputs look visually dramatic. Analysts should always check absolute coin quantity and market value alongside CDD.
Methodology and interpretation
Interpret coin-age metrics with entity and destination context where available. Exchange inflows following old-coin movement carry a different implication from migration into an identified self-custody or custody address.
| Question | Why it matters | What to verify |
|---|---|---|
| How old are the coins? | Age weighting is the core signal. | Age bands and CDD contribution. |
| Where did they move? | Custody transfer and exchange deposit differ. | Destination labels and entity heuristics. |
| How large was the quantity? | A tiny ancient output can look dramatic in age terms. | Coin amount and market value. |
| Was there wallet maintenance? | Consolidations can destroy large coin-day totals. | Transaction structure and known entity behaviour. |
Use rolling averages, percentiles or cohort distributions to avoid overreacting to isolated ancient-wallet events. One dormant whale moving does not necessarily describe broad long-term-holder behaviour.
Cohort-normalised views can help distinguish a broad change in spending age from one exceptional ancient UTXO. If dormancy rises across several age bands and many entities, the signal is structurally broader than a spike caused by one address.
Pair CDD and dormancy with realised profit/loss and exchange-flow data. If old coins move, realise large gains and enter exchange-labelled wallets during high spent volume, the case for genuine distribution is stronger than age data alone.
Worked example
Five BTC held for 800 days are spent. They destroy 4,000 coin days. On the same day, 1,000 BTC held for only two days destroy 2,000 coin days.
The smaller 5 BTC movement has greater age weight, but it is not necessarily more economically important. If it moved to a new wallet controlled by the same holder, calling it distribution would be unjustified.
The example shows why age-weighted activity and absolute value should be read together. Old-coin movement is notable, not self-interpreting.
Now imagine daily CDD spikes to a one-year high, but 85% of the contribution traces to one known custodian migrating cold-storage infrastructure. The headline “old coins are moving” is factually true; the inference “long-term holders are selling” would still be unsupported.
Common mistakes and misunderstandings
- Assuming dormant coins moving means holders sold.
- Ignoring absolute coin value while focusing only on age weight.
- Failing to identify wallet consolidation or custody migration.
- Using one isolated old-wallet event as a broad holder-behaviour conclusion.
Practical workflow
- Check the exact CDD or dormancy formula used by the provider.
- Inspect quantity, age and destination of major contributing flows.
- Compare with exchange inflows and realised profit or loss.
- Use rolling distributions to judge whether activity is genuinely unusual.
- Separate ownership-change evidence from mere movement of old coins.
✅ Knowledge checkpoint
- How can 5 old BTC destroy more coin days than 1,000 recently moved BTC?
- Why does old-coin movement not prove selling?
- What additional data would strengthen a distribution interpretation?
- Why can wallet consolidation create large CDD without economic turnover?
FAQs
❓ What is one coin day?
One coin held or unspent for one day.
❓ What destroys coin days?
Spending or moving the relevant UTXO resets its age under the metric.
❓ Is high CDD bearish?
Not inherently. It shows older coins moved; destination and ownership context determine the economic meaning.
❓ What does dormancy add?
It relates age-weighted spending to transaction or spent volume to characterise the average age of moving coins.
📋 Summary
Coin days and dormancy reveal the age structure of spending. They are valuable for spotting unusual movement of old supply, but destination, ownership and transaction structure determine whether that movement represents distribution, custody migration or wallet maintenance.
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