"Job satisfaction is especially high among those 65 and over because most people working at that age are not forced to still work, due to financial reasons, but choose to do so because they like their jobs," Tom Smith, who led the study, said in a statement.
Of the 27,587 people interviewed between 1972 and 2006 for the study, 86 percent said they were satisfied in their work and 48 percent said they were very satisfied.
Among the over-65 age group, nearly three-quarters of those surveyed said they were very happy in their jobs.
Lack of job satisfaction was more pronounced among unskilled, low-paid workers, the study showed.
Just over one-third of unskilled workers said they were very satisfied in their jobs, compared with more than half -- 53 percent -- in prestigious jobs.
And only 40 percent of workers earning less than 12,500 dollars (9,000 euros) a year said they were very happy in their work, compared with more than two-thirds of those in jobs that paid more than 110,000 dollars annually.
The poll also showed an ethnic trend in job satisfaction, with more than half the white people polled saying they were very happy in their work, compared with 46 percent of Hispanics and 40 percent of African Americans.