The world's top oil producers are proving unable to put more barrels on thirsty world markets despite sky-high prices, a shift that defies traditional market logic and looks set to continue.

Fresh data from the U.S. Department of Energy show the amount of petroleum products shipped by the world's top oil exporters fell 2.5% last year, despite a 57% increase in prices, a trend that appears to be holding true this year as well.

There...