(Bloomberg) -- The cost of shipping freight in the U.S. continued to rise in August as equipment and labor capacity constraints persisted.

A measure of freight rates jumped 26.6% from a year earlier, the sharpest increase since February 2006, based on the latest figures from Cass Information Systems. The gain followed a 23.8% increase in July and marked the third straight month of acceleration.

The volume of shipments by road and rail increased 12.2% from a year earlier, the smallest annual gain since March. At the same time, the group’s gauge of the amount spent on shipping freight surged 42.2% from August 2020.

While limited by intermodal capacity and a tight labor market, shipping volumes remain elevated. The Cass shipments index is at its second-highest point since 2018.

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