In 1696 the British began to keep records of their imports and exports in terms of money values. For this purpose, tables of prices were prepared first for England, and subsequently for Ireland and for Scotland, with the rates based, it is said, on market conditions at the time. Some adjustments in the initial valuations were made in the early years, but thereafter, for over a century and a half, the same prices were used in calculating “official” values. For imports and re-exports they supplied the sole basis for computing money values throughout this period. For exports of domestic produce and manufactured goods, however, a concurrent series of declared values was begun when a convoy tax was imposed ad valorem in 1798; but this series, though continued after the war, has been overshadowed by the “official” valuations which attained something of the respectability of a time-hallowed tradition. Year after year through peace and war, dearth and plenty, high prices and low, the clerks meticulously multiplied their quantities by these unchanging rates. In other words, British “official” trade values became progressively more useless as measures of current market values until the system was reformed in 1854. As a result, historians and economists are faced with frustration or distortion in any question dependent on a fairly accurate knowledge of the course, or the terms, or the balance of British trade in the period.