Fidelity recently released a study looking at Americans in this demographic breakdown:
Generation Y: born from 1981 to 1988
Generation X: born from 1965 to 1980
Baby boomers: born from 1946 to 1964
“Matures:” born from 1909 to 1945
Here is the Executive Summary from the research: Fidelity® Five Years Later Research
Here is an infographic for Gen Y.
Here is the press release.