Final answer:
City planners need data on region and population demographics, such as gender, marital status, race/ethnicity, and socioeconomic status, in order to determine where to place services like schools and playgrounds.
Step-by-step explanation:
City planners who want to know where to put services such as schools and playgrounds need data about region and population demographics. By analyzing the region, they can identify areas with high population densities and/or areas with a high concentration of families. Gathering data on population demographics, such as gender, marital status, race/ethnicity, and socioeconomic status, can help determine the specific needs and preferences of different groups within the population.