The $453.5 billion U.S. e-commerce market is built on the back of consistent and accurate fulfillment pipelines.

As online retailers have upgraded their capabilities, they’ve driven consumers to expect inexpensive or free shipping options, speedy delivery, and easy returns. And, increasingly, consumers are conditioned to expect options such as in-home delivery, in-store returns and same-day delivery.

These conditions all conspire to drive up retailers’ fulfillment costs. E-commerce logistics costs—including transporting products to fulfillment centers, delivering to customers, warehousing products, processing returns and carrying inventory totaled $117.2 billion last year, according to an estimate by supply chain consultancy Armstrong & Associates. That’s roughly a quarter of total U.S. e-commerce revenue.

This is a preview of findings from the “2018 Click, Ship & Return” report from Internet Retailer’s research department, which will be released in September 2018.