New disclosures showing the pay gap between corporate America’s top executives and typical workers are likely to take a less-is-more approach, according to a soon-to-be-released Mercer survey.

Virtually all (87 percent) of companies that are readying such reporting this year said they don’t plan to provide much more than the required ratio comparing what their chief executive officer makes to how much their median employee gets paid. That ratio is 200-to-1 or less for most of the 144 companies surveyed...