Among recent retirees, the top consideration in leading themto leave the workplace was not their employer'sretirement program.

Instead, according to a Towers Watson survey, workplacedisengagement and workers' eligibility for Social Security and Medicaretopped the list.

In addition, 20%of those recent retirees said one of the key factors in theirdecision was disengagement with their jobs.

One reason the report said it's important for employers tounderstand what drives people to retire is that, in the comingflood of boomer retirees, employers will have to be able to managethe departure of employees who are in critical positions.

Other factors include the changing role of employers and thewaning traditional model of full retirement age at a fixeddate.

While data are available on some of the factors that causepeople to retire — such as age, health, family circumstances andemployer incentives, all of which can vary in importance with theage of the worker — there isn't so much information available onthe thought processes and motivations leading up to retirement.

While more than a quarter of respondents listed employerincentives, such as retirement eligibility and retiree healthbenefits, as their main motivation, more recent retirees werefocused on other things.

And as employers cut the benefits available to retirees, theyhave less sway over workers' decisions to retire.

In addition, there's the question of how retirees felt afterretirement.

Those who felt pushed out by the pressures of work were morelikely to say that they were worried about their finances; theywere also more likely to be shocked by retirement and be sorry theyleft the job.

Among those who cited reasons related to their workingenvironment, the overwhelming majority said that feeling disengagedfrom their employer, their job or both played a pivotal role intheir retirement decision.

On the other hand, those who retired to take advantage ofemployer incentives, or because they were eligible for employerbenefits, were less likely to regret their decision.