reduplication for distribution (一人一人)

A reduplicated noun pattern (NN) used to express distributive 'each X individually / one X at a time' — 一人一人 ('each person'), 一つ一つ ('each one'), 一歩一歩 ('step by step'), 日々 ('day by day'), 人それぞれ ('each person their own'). Common across many counters and time units. Signals that an action applies to each member separately rather than to the group as a whole.