Chain transfer in chain polymerization

In chain transfer in chain polymerization, a growing chain can lose its polymerization-active site while another molecule acquires reactivity. In a common atom-transfer picture, the old chain becomes inactive and the new carrier can initiate further chain-growth propagation.^[ref] The number of reactive carriers can survive even though the identity of the growing chain changes. If the new carrier successfully starts a new chain, $C$ increases; a fixed active-carrier count therefore does not imply a fixed polymer molecule count. Whether transfer is irreversible, reversible, or involves an already existing chain matters for the final bookkeeping.