A significant increase in the seaborne trade for coal over the past 20
years has unified formerly separate coal markets into a world market
in which prices move in tandem. By virtue of its large domestic market
, the USA has become the residual supplier and price setter in the wor
ld coal market. Changes in multifactor productivity have been the prim
ary cause of the long-term fluctuations in coal prices that have been
observed in the USA since the end of the Second World War and in the w
orld coal market.