Share of supply by how long the coins have not moved
Each band shows what share of all bitcoin last moved that long ago. Together the bands add up to 100% of supply, so the chart reads like a geological cross-section: what matters is not how high a line sits but how thick a band is.
When the lower, warm bands swell, old coins are moving into new hands — that accompanied the top of every cycle so far. When the upper, cold bands thicken instead, the market is holding and free supply is drying up; that is what bear markets and early bull phases look like.
The 10 years and older band also contains coins nobody holds the keys to. Lost bitcoin is indistinguishable on-chain from merely forgotten bitcoin, so the oldest band never falls to zero.