The present invention is directed to utilizing monitoring devices (200) for determining the demographics of individuals passing a particular geographic location. The monitoring devices (200) are distributed to a number of study respondents. The monitoring devices (200) track the movements of the respondents whose demographics are known. While various technologies may be used to track the movements of the respondents, at least some of the location tracking of the monitoring devices (200) utilize a satellite (105) location system such as the global positioning system (“GPS”). Geo data (movement data) collected by the monitoring devices is analyzed by a post-processing server (400) that determines the demographics of the study respondents that pass a chosen geographic location.