I feel grouping groups of 18 to 40 year olds (or any other arbitrary starting and ending age depending on the definition of millennial we're using) as one category called Millennial is one of the most confusing terms. You can't even use it as a scientific classification or categorization or even define a person properly using the word Millennial because definitions vary and the person could be 20, 30 or as in this article, 36.