Under the ADEA, there has to be a valid reason -- not related to age -- for all employment decisions. Examples of valid reasons would be poor job performance by the employee or an employer's economic trouble. In the case of layoffs, a company cannot use age as the basis for determining who is laid off and who is kept on. If most people who are laid off are 40 or older, and the majority of workers kept on are younger, there may be a basis for an ADEA complaint or lawsuit, especially if the employer has hired younger workers to take the places of workers over 40.