In this dataset, Chicago population is divided by Geographic location - zip code of the city. Furthermore, the population is divided according to age group, sex and race.

The following notes are found on the webpage - Chicago Population Counts, from where the dataset is exported.

Population totals for groupings commonly used in other datasets.

Not all values are available for all years.

Note that because the "Citywide" rows roll up the values from the individual ZIP Codes and the "Age 18+" and "Age 65+" columns overlap other age categories, as well as each other, care should be taken in summing values to avoid accidental double-counting.

Data Sources: U.S. Census Bureau American Community Survey 5-year estimates (ZIP Code) and 1-year estimates (Citywide)