The digital divide between developed countries and many emerging economies is increasing because of the high cost of digital access, according to a new report published Wednesday by the World Economic Forum.

The top-ranked countries—the U.S., Scandinavian nations and Singapore—were mostly unchanged this year from 2015, while many large developing countries such as India and Mexico saw their rankings drop, according to the Global Information Technology Report. The annual study measures countries’ readiness to reap the rewards...