This paper investigates the demographic differences in day-by-day mobility and activity spaces of human beings. We develop a novel nonparametric density ranking approach to measure activity space and mobility patterns. Specifically, as a case study, we examine the difference between males and females in their mobility patterns: the distance and frequency of travel as associated with their activity spaces, which are the speed of travel, areas of frequent visits and significant time spending. With this nonparametric approach, we are able to more accurately identify the mobility and activity traces as indicated by longitude/latitude pairs in GPS data. Importantly, these two measurements shed light on the contextual conditionals males and females expose to, and explain the gender discrepancies in various socio-environmental outcomes. Results show that males have a higher instability and degree of mobility, and a less structured activity space. These results correspond to the sociological and demographic theories on institutional effects, neighborhood effects and conditional exposures.