(3BL Media/Justmeans) â The Millennial Generation, or Gen Y, are the demographic cohort following Generation Xâmost researchers use birth years ranging from the early 1980s to the early 2000s for this group. There is a shared view that Millennials are more aware of society's many challenges than previous cohorts, are looking for a broader social purpose, and, in America, they are now the most populous generation.