Now let's look at the individual markets in more detail starting with coal. Coal revenue declined 9% in the quarter to $679 million. Domestic coal tonnage declined 9% impacted by continued high stockpiles in our service territory. Export coal tonnage increased 6% as shipments of metallurgical coal increased compared to a weak prior year quarter. Finally, total revenue per unit was down 4% with lower export pricing more than offsetting domestic pricing gains.
Next, let's look at the merchandise business. Overall, merchandise revenue increased 10% to over $1.8 billion in the quarter. Volume in the agricultural sector was up 5%. Feed grain shipments, both domestic and export increased sharply due to a strong 2013 harvest. In addition, ethanol shipments grew as lower corn prices resulted in higher ethanol productions. The construction sector grew 4% overall as the continued recovery of the residential housing market drove increased shipments of building products. In addition, industrial waste volumes were strong, due to an increase in shipments associated with large scale remediation projects. Finally, the industrial sector was up 10% on the strength of energy-related commodities including crude oil, liquefied petroleum gas, and frac sand.
Moving to the next page, let's review our intermodal business. Intermodal revenue increased 10% to $437 million. Domestic volume was up nearly 13%, setting a new quarterly CSX record, driven by growth with our existing customers and continued highway to rail conversions. International volume was up 9% year-over-year on growth for the existing customers, new service offerings, and a favorable comparison to the fourth quarter of 2012, when shipments were disrupted by Hurricane Sandy. Total intermodal revenue per unit declined 1% as continued solid core pricing gains were more than offset by the lower fuel recovery mix.
Finally, 90% of our intermodal traffic is now moving in lanes that are double-stack cleared. That number will continue to grow through strategic network investments, most significantly the Virginia Avenue Tunnel clearance project in Washington, D.C.
Now let's turn to the outlook for the first quarter. Looking forward, we expect stable to favorable conditions for over 90% of our markets, and the overall volume outlook for the first quarter is positive. Looking at some of the key markets, agriculture is favorable, with higher year-over-year crop yields supporting continued growth in grain shipments. The outlook for the automotive market is also favorable, as North American light vehicle production continues to grow. We expect growth in chemicals, as we continue to capture opportunities created by the expanding domestic oil and gas industry.
We expect our domestic coal volume will grow in the first quarter, as we cycle our relatively weak first quarter in 2013. At the same time, our outlook for full year domestic coal volume is neutral. But the average length of the haul will be shorter this year and will contribute to our lower overall revenue per unit.