Per-block TAO bought directly into each subnet's pool over the last 24 hours. Chain buys are the protocol-injected demand that funds subnet emissions — the cleanest leading indicator for which subnets the network is actually paying for.
The chain-buy figure is the amount of TAO the network has injected into each subnet's alpha pool over the last 24 hours via emissions. Validators direct emission weights toward subnets they back; the pool absorbs that TAO as buy pressure and mints alpha against it. High chain buys mean validators are routing real economic demand into a subnet — independent of any open-market price action.
Numbers come from subnetTaoInEmission aggregated over 7,200 blocks. Same source taomarketcap.com uses for its “Chain Buys” column.