By how much did the cost of governmental barriers to trade change over the 20 th century, and how might they change by the middle of the 21 st century? This paper addresses that question by first reviewing evidence on the changing extent of global trade restrictions since 1900, particularly for agricultural and manufactured goods.
It then assesses prospects for trade policy changes over the coming four decades by drawing on current political economy theory and evidence. The paper then provides crude estimates of the annual cost, in terms of economic welfare foregone in highincome and developing countries, of those trade-restricting policies.
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