The 22-year-old North American Free Trade Agreement has been a controversial topic in the presidential campaign for its impact on the U.S. economy, but the latest freight data from the Department of Transportation shows a continued decline in shipments between trading partners.

The DOT reported on Thursday that the value of U.S. freight with Mexico and Canada declined for the 17th consecutive month in year-over-year comparisons. Trucks carried more U.S. freight by value with NAFTA partners in May compared to a year earlier, but declines in all other freight modes led to a 3.1 percent decrease to $89.8 billion in the total dollar value of cross-border freight from May 2015, according to the Transborder Freight Data from DOT’s Bureau of Transportation Statistics.

The value of commodities moving by truck increased 1.3 percent, as the value of incoming freight from Mexico, up 6.2 percent, and Canada, up 11.4 percent, exceeded the 5.5 percent decrease in shipments from the U.S. Of the top 10 commodities transported between the U.S. and other NAFTA countries by truck, fruits and nuts had the highest year-over-year increase — 13.2 percent.

The value of freight carried on other modes declined — rail by 3.1 percent, air by 3.8 percent, pipeline by 21.4 percent and vessel by 30.7 percent. A drop in the price of crude oil played a key role in the large declines in the dollar value of products shipped by vessel and pipeline.

Trucks carried 66 percent of U.S.-NAFTA freight and continued to be the most heavily utilized mode for moving goods to and from both U.S.-NAFTA partners. Trucks accounted for $31.2 billion of the $47.9 billion of imports and $28.1 billion of the $42 billion of exports.

Rail remained the second-largest mode by value, moving 15.8 percent of all U.S.-NAFTA freight.

From the 12 months through May, the value of U.S.-Mexico freight rose 0.1 percent to $43.9 billion as all modes of transportation except truck and rail carried a lower value of U.S.-Mexico freight than a year earlier. Freight carried by truck and rail both increased 2.3 percent. Air freight value declined 5.3 percent. Pipeline and vessel freight value dropped by 9.6 percent and 18.8 percent, respectively, both due mainly to lower crude oil prices.

From May 2015 to May 2016, the value of U.S.-Canada freight flows fell 6 percent to $46 billion.

In May, the top commodity category transported between the U.S. and Mexico by all modes was electrical machinery, of which $7.6 billion, or 91.6 percent, moved by truck. The top commodity category transported between the U.S. and Canada by all modes was vehicles and parts, of which $5.1 billion, or 55.2 percent, moved by truck and $3.9 billion, or 42.4 percent, moved by rail. Apparel was not among the top export categories from either country.