observations on multiple phenomena collected over multiple time periods for the same group of individuals or other units. Repeated observations permit the researcher to study the dynamics of change using techniques such as time-series analysis. Panel data have characteristics of both longitudinal data and cross-sectional data (see cross-sectional analysis). For example, the values of the gross annual income for each of 500 randomly chosen households in New York City collected for each of 10 years would be panel data.