Then there is Myers-Briggs, perhaps the best known psychological test, and Development Dimensions International (DDI), a business assessment firm whose clients include Citibank, Microsoft, and Phillip Morris. One of the largest companies in the field, DDI has seen its value soar over the past five years. Doug Reynolds, vice president of assessment technology for DDI, estimates their management assessment sector’s revenue to be $80 million last year. “We now have assessment centers around the world, and each center can test 10 to 15 executives at a time,” Reynolds says. “There’s been a tipping point where [companies] are understanding that they should use actual data to make decisions about people. If you rely only on your gut, you make a classic mistake.”

Of course, screening can’t predict all potential problems. One of DDI’s clients, JetBlue, is still reeling from a recent series of public relations disasters when storms caused thousands of passengers to be stranded in airports or trapped on planes that were unable to take off for hours at a time. David Neeleman, JetBlue’s founder and C.E.O. since 1998, stepped down earlier this month. He will remain chairman, though, and denies the move is related to recent company problems.

Even so, JetBlue continues to tout its friendly workforce and to use the latest assessment techniques to help preserve it. When interviewing for management positions, JetBlue uses DDI’s behavioral diagnostic questions to evaluate whether candidates will exhibit and promote the five qualities essential to the corporate culture—“safety, caring, integrity, fun, and passion,” according to Vincent Stabile, JetBlue’s senior vice president of people. “We want to know whether or not those five values come naturally to that individual,” says Stabile. “We’re looking to see that an individual has the skills and experience for the job and can fit into our culture in a good way.”

But JetBlue isn’t just focusing on hiring and promotion. Like a growing number of other companies, it also uses personality assessments to develop the best and the brightest. Two years ago, the organization began using the Myers-Briggs test in its leadership training course, combined with a 360: Following the exam, managers sit down with coaches and put together development plans to work on their weaknesses. “There’s much more of a focus on individual performance and psychology, on understanding how you can help them to become better leaders. People are understanding that it can have a tremendous impact,” says Stabile.

Dell also uses diagnostics in their training. They give future leaders the 360 exam and then evaluate them on 20 to 25 competencies ranging from financial and business acumen to dealing with ambiguity, says Amy King, a company spokeswoman. “Then we identify opportunities to help them develop the skills and experience to get them on the right track,” she says.

Had Dunlap, Ebbers, and Lay been subjected to such an exhaustive examination, corporate America might be a very different place. Then again, without them, the psychological testing industry may never have grown into the healthy business it is today.