Container ship lines are poised to break a years-long pattern of vessel capacity expanding faster than cargo volume but only if they avoid another ship-ordering binge, Dynamar says in a report profiling the 25 largest global container lines.

The Netherlands-based research and consulting firm said its “Cap/Car Index” widened steadily for several years through 2009. The index compares expansion in vessel capacity and cargo carryings from a 1999 base. A reading below 100 indicates that capacity has grown faster than cargo volume.

From a reading of 91 in 2005, the Dynamar index fell to 88 in 2006, 87 in 2007, 81 in 2008 and 73 in 2009, when global container volumes plunged by double digits during the recession while carriers added scores of new ships.

“Even when taking all the effects influencing this ratio into account, the conclusion can only be that the world’s largest carriers are expanding capacity at a faster pace than the general growth of volumes justifies,” the report said.

Dynamar said current shipyard order books and economic developments suggest the capacity-to-carryings ratio will narrow in the next couple of years.

The report said capacity is expected to grow 8 to 9 percent annually through 2012 before slipping to 5 percent in 2013, while cargo volume is projected to rise 10 to 11 percent for 2011 and 2012 and 8 to 9 percent in 2012 and 2013. But the report added, “Any renewed large-scale ordering as seen in 2006-2007 would push the Car/Cap Ratio further back down.”