A measure of total for-hire freight movements in the U.S. fell for the second straight month in April, according to a report issued Wednesday by Transportation Department.

Its Freight Transportation Services Index (TSI) fell 0.6% in April from March after reaching an all-time high in February and is down 2.3% since then. When April is compared to the same time a year ago it increased 0.8%.

The March index was revised downward to 123.5 from 124 in last month’s release while the February figure was also revised down slightly.

The Freight TSI, which is seasonally-adjusted, measures the month-to-month changes in for-hire freight shipments by mode of transportation in tons and ton-miles, which are combined into one index. It measures the output of the for-hire freight transportation industry and consists of data from for-hire trucking, rail, inland waterways, pipelines and air freight.

The April decrease in the Freight TSI was broad based, with declines in all freight transportation modes except air freight and trucking.

According to the department, the decrease took place despite growth in other economic indicators in April. The Federal Reserve Board’s Industrial Production index grew by 1% with growth in manufacturing, mining, and utilities while employment and personal income both grew in April. However, housing starts declined, while the Institute for Supply Management’s Purchasing Managers’ Index showed positive but slowing growth.

The two-month decline in the index represents the third time it has decreased for two months in a row since the beginning of 2015, though it represents a more modest decrease than that of August/September 2016.

The Transportation Department said research has shown a clear relationship between economic cycles and the Freight TSI as well as its separate Passenger Transportation Services Index.