For many of today's workers, retirement does not mean the end of work.

Rather, they're entering a phase called "bridge employment," which economists describe as the period between leaving a career job and fully retiring.

Boston College economist Joseph Quinn says his research shows retirement for many seniors occurs over time, rather than as a single event. He attributes this to a changing economic picture.

Bridge jobs often have lower pay, but Quinn says seniors are taking them voluntarily because they offer advantages like flexible hours and part-time work.

According to the University of Michigan's Health and Retirement Study, roughly 6 of 10 people of retirement age plan to stay in the workforce after leaving their career jobs.