Brief 3 described workers as a component of the population and provided a comprehensive overview of changes in the workforce as they relate to the demographic characteristics of the population. Brief 4 provided more detailed descriptive data covering the geographic location of workers. Not surprisingly, there is a strong inherent relationship between jobs and workers—neither can exist without the other, at least not for any length of time. At the national level, aggregate disparities between jobs and workers can be explained by measures of vacant positions and unemployed workers. These measures do not add particular insight when trying to understand commuting trends. However, at more detailed levels of geography, there can be significant variations between the nature and counts of jobs and counts of appropriately credentialed workers, and these disparities can influence commuting patterns as workers travel to fill available positions. Brief 15 discusses the flow of workers between geographies; this brief provides summary information on the location of jobs by geography.