Companies that reward employees with ownership stakes have an edge over those that don’t, according to a new study of nearly 57,000 companies around the world.

Employee ownership, including defined-contribution plans with substantial holdings in the employer’s stock, profit-sharing policies and stock-bonus programs, can boost corporate profits by as much as 4%, says Ernest O’Boyle, a professor of management and organizations at the University of Iowa and co-author of Employee Ownership and Firm Performance: A Meta-Analysis, a paper published in the Human Resources Management Journal.

“The consistency of the effect really surprised me,” Dr. O’Boyle says. “Although the effect is small, it’s pretty darn robust.”

“Our results suggest that a firm with $1 million in profits could realize an increase of $40,000,” the authors conclude.

The study is the first of its kind in more than two decades, and one of the few analyses to illustrate that worker ownership can have “a small, but positive and statistically significant relation to firm performance,” the authors write.