For each generation that are born, there is a period of years where they enter the workforce. After a period of time, they hit the peak of their careers. For a professional, it is assumed to be when they are 45 years old. Retirement is at age 65.
There is a distinct drop in birth between the Boomer Generation and the Gen X. Therefore, there will be a lack of workers to fill the positions. After Gen X, there is a jump in population again for the Gen Y. There is an overlap between retirement of the Boomer Generations, and when the Gen Y hit their peak professional years. Boomer Generation is set to retire from 2010 to 2030. In the middle of that retirement period of Boomer Generations, Gen Y will hit their peak professional years starting 2025 until 2040. Therefore, Gen Y can cover the gap left by the Boomer Generations. There are a lot of interest in mentoring the Gen Y because they are set to pick up after the Boomer Generations. That leaves the Gen X. They are the low birth number generation. They are the fogotten generation. They are holding onto the jobs until Gen Y come on line.
Silent generation: 1925-1945
Baby Boomers: 1946-1964
Gen X: 1965-1979
Gen Y: 1980-2000