Available with Business Analyst license.
Component geographies are boundaries selected within larger boundaries, for example, block groups inside a drive-time boundary. In most cases, the boundary layer will be a Business Analyst trade area.
Some examples include:
- Create an output feature class that includes all the ZIP Codes that intersect a drive-time trade area.
- Create a trade area of all the County Sub Divisions within a given county. In most cases, the correspondence between a parent and child geography is a strict hierarchical, one-to-many relationship.
Component geographies can be created using these different selection methods:
- Centroid Within
- Completely Within
The find component geographies tool gives you the option to calculate the statistical ratios of the underlying geographies. For example, you create component geographies of all ZIP Codes within a county. You can use the Calculate Ratios option to determine what percentage of ZIP Codes exists within the county boundary. Ratios for population, households, housing units, business counts, and general area can be generated. The ratio output appears in the trade area attribute table.
You can calculate ratios in the following ways:
- Area ratios only: This method means that a percentage will be calculated only where subgeographies intersect the boundary layer (for example, the percentage of area for each ZIP Code boundary within a county boundary).
- Area ratios plus population, housing units, and businesses: This method means that a percentage will be calculated only where component geographies intersect the boundary layer (for example, percentage of area for each ZIP Code boundary within a county boundary).
Output is based on a polygon-to-polygon selection.
The image below is a typical output with the US Census Tracts represented in red and their centroid within ZIP Codes in black. You can automatically calculate the area, demographic and business ratios of component geographies.
The attribute table below shows the Area ratios plus population, households, housing units and businesses option for ZIP Code within a county. In the Ratio field, the Fife Lake ZIP Code (highlighted in green) is 14.32% contained in the county boundary but 32.6% of its population resides within the county as does 33.6% of total households. The Grawn ZIP Code (2nd from top) is 100% contained in the county boundary. Note - the Mesick ZIP Code is 0% contained in the boundary. It can be zero percent because the ZIP Code boundary touches or intersects the county border but is not within the county. The ratio fields are POP (Population), HH (Households), HU (Housing Units) and BUS (Business Counts).
Learn more about Find Component Geographies (Subgeography).