Over the last 10 years, thousands of businesses across the country — from big corporations to storefront shops — have used arbitration to create an alternate system of justice. There, rules tend to favor businesses, and judges and juries have been replaced by arbitrators who commonly consider the companies their clients, The Times found.

But in interviews with The Times, more than three dozen arbitrators described how they felt beholden to companies. Beneath every decision, the arbitrators said, was the threat of losing business.

Fearful of losing business, some arbitrators pass around the story of Stefan M. Mason as a cautionary tale. They say Mr. Mason ruled in favor of an employee in an age discrimination suit, awarding him $1.7 million, and was never hired to hear another employment case.