According to a new research study by the Sloan Center on Aging & Work at Boston College, the people who are most satisfied with their jobs are older employees – those age 50 and up. The most dissatisfied? Those between the ages of 30 and 39.

Furthermore,employees age 40 and older are the most engaged and show the highest level of organizational commitment,according to the study,while those under 30 are almost as satisfied as the most satisfied group of 50 and older.

The study based its conclusions on work experience data from 11,298 individuals working for seven multinational companies at 24 worksites in 11 countries. 

So why is the 30-39 group so dissatisfied?

“That is the stage of life where people typically start a family and have young kids at home,” says Wharton marketing professor Cassie Mogilner. “Therefore, these people are more likely to feel the strains of balancing work and life, thus pulling their minds away from being fully engaged” on the job. In addition, notes management professor Nancy Rothbard, this age group “is in an intense career stage where they are often engaged in continued on-the-job learning, with greater responsibilities.”

Peter Cappelli, director of Wharton’s Center for Human Resources, notes that “life satisfaction seems to hit bottom [right around] age 30,” and may be related to the fact that these employees’ “expectations are not being met.”

But as employees’ children get older,says Mogilner, “those who are career oriented can get their minds back in the game and enjoy greater satisfaction from their work. Jobs provide a great source of self-definition,particularly when people are young and starting out their careers — and identifying what careers they want to pursue — and then again when they have fulfilled the toughest years of parenting.

“Employees who are working later [in life] and who are most satisfied with their jobs may reflect a case of self-selection,” she adds. “Usually by one’s 50s,if [a person] is working,she has likely climbed up the ladder to be successful in her profession. This group is likely to continue to work if they like what they do.”

As for Wharton management professor Matthew Bidwell, he is “a bit surprised by the results. My impression was that generally workers got more satisfied as they got older, and that the main reason for this was that they were generally moving into more rewarding jobs with higher pay and more responsibility. So I would expect job satisfaction to be lower for those under 30. In fact, if you look at the study, there doesn’t appear to be a statistical difference between the under 30s and the 30-39 year olds. So the results are consistent with the standard finding of job satisfaction increasing over time.”

Does the survey’s finding – that those over 50 are the most satisfied,and those over 40 the most engaged and committed – go against conventional wisdom that older workers are not as valuable as younger ones? What can be inferred from the study’s conclusions depends on what measure of engagement the authors used, says Rothbard. “It sounds like they used commitment as a proxy for engagement. So I think this more reflects the fact that those over 40 are more satisfied and committed to the organization,which can lead to greater workforce stability as it is negatively related to whether people leave.”

Bidwell says he wouldn’t “draw too much of a straight line between the commitment and value to the firm. Workers can be highly committed but also bad at their jobs, and vice versa. I’m not sure on the conventional wisdom about age. There are concerns that older workers will be less flexible than younger ones,but along many other dimensions including maturity, stability,knowledge, etc., you would expect them to outperform younger workers.”

Does the stalled economy affect these results, by, for example, creating a need for older workers to stay in their jobs longer,even as companies cut back on pay and promotions? Or is the 30 to 39 cohort always pretty dissatisfied with their lot? “I don’t think this is related to the stalled economy per se,” says Cappelli. “After all, it’s stalled for everyone.”