A drill hierarchy defines the paths that people can use for data drilling within a report or spreadsheet. It is a predetermined set of data groupings at multiple levels, with the summary data at the top and progressively more detailed subgroups of data below. Drill hierarchies are often based on geographic regions or units of time. For example, descriptive analysis in a report might show ecommerce sales for the last month. To analyze the data in more detail, you could drill down through the hierarchy to examine sales for specific days, hours within each day and even minutes within each hour.