Imports are flat from the East Coast to the West Coast as we head into the peak shipping season, and that inactivity is largely due to increased e-commerce.

This is the second year in a row without the traditional late summer peak in shipping traffic and economists say the nation’s empty docks are a sign that retailers are cutting down their supply chains as more consumers choose to shop online, the Wall Street Journal reports. Companies like Target and Lowe’s are already moving away from keeping stores constantly stocked with goods and towards keeping more goods in warehouses.

The shift is taking the transportation industry completely by surprise—just when ports across the country are spending billions upgrading equipment and depending harbors, US ports are on track to handle only 2.2% more imports this year. That’s the slowest rate of growth since 2011. [WSJ]