This paper examines why firms sometimes employ older workers, but tend to not hire new older workers for the same job. It focuses on one aspect of that phenomenon: the propensity for firms to fill jobs from the inside rather than hire someone new from the outside. Using a survey of establishments with information on a white collar job currently held by an older worker, the paper tests hypotheses on what types of jobs are likely to be filled from the outside. Several of the results point to the potential importance of asymmetric information, whereby the firm has better information on key characteristics of insiders versus outsiders.