The innovation of the British credit system and issuance of banking bills allowed the American traders to clear their debts with co-hong merchants and gradually substitute their cargoes away from carrying specie and more towards domestically manufactured items. The Americans could then later pay off the principal and interest on their loans to the British banks. From 1830 to 1850, faster and larger tea clippers were introduced, thereby replacing the earlier, smaller privateering vessels from the American Revolution. As a result, Americans could achieve greater scale with the combination of tea clippers and British credit. Tea could be transported to American markets in less time and with greater freshness, translating into higher profits. By 1834, tea accounted for over 80% of the American trade from China.