Lipperman-Kreda S, Finan LJ, Kowitt SD, et al. - Researchers sought to determine the association of daily exposure to tobacco outlets within activity spaces with cigarette smoking and with the number of cigarettes smoked by youth that day. For collecting real-time data of participants’ environments and behaviors, they analyzed Geographic Ecological Momentary Assessment data that combined daily surveys with ecological momentary assessment of global positioning systems using geographic information systems. In the setting of eight mid-sized California (USA) city areas, they included 1,065 days in the analytic sample, which were clustered within 100 smoker and non-smoker participants (16-20 years old, 60% female). Observations seemed not significantly supporting the association of differences in day-to-day exposure to tobacco outlets within activity spaces with whether a person smokes a cigarette on a given day among young people in urban California USA, however, there appeared a positive correlation of higher exposure to tobacco outlets with the number of cigarettes smoked on that day.