Even once unloaded, containers piled up on docks unclaimed, because of a shortage of truck drivers needed to haul cargo to warehouses. Truck drivers had long been scarce, with wages steadily eroding over the years amid grueling working conditions.

Businesses across the economy struggled to hire workers: at warehouses, at retailers, at construction companies and for other skilled trades. Even as employers resorted to lifting wages, labor shortages persisted, worsening the scarcity of goods.