Mobile web is booming: We forecast that US retail sales via smartphone will grow at a compound annual growth rate (CAGR) of 18% over the next five years. Plus, smartphones will impact more than one-third (or more than $1 trillion) of total US retail sales at some point in the customer journey in 2018. This report shares examples of how leading retailers' mobile websites approach critical functionality and usability challenges. It follows up on the recommendations we made in The Forrester Retail Wave™: US Mobile Web, Q4 2017.