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Understanding District Overlaps
This feature measures how much of one jurisdiction’s population overlaps with another, based on the 2020 Census (Adjusted P.L. 94-171) block-level data. It provides insight into how districts and jurisdictions share populations and helps answer questions like:
- What percent of my city’s population is in Assembly District X?
- What percent of Assembly District X is made up of my city’s residents?
How It Works
- Each jurisdiction is made up of many small census blocks, and every block has a recorded population from the 2020 Census.
- When two jurisdictions share the same census blocks, we calculate the shared population proportionally, based on how much of each block belongs to each jurisdiction.
- Instead of treating block overlaps as all-or-nothing, we use actual geographic boundaries to determine how much of a block belongs to each jurisdiction. This ensures more precise population estimates for overlaps.
- We only display overlaps where at least 2% of a district’s population is shared, keeping the tables clear and relevant.
Why This Matters
Seeing how jurisdictions intersect at the population level helps you understand how communities are split or combined across local and legislative boundaries. For example:
- A county might be divided among several Assembly Districts, each containing a different proportion of the county’s residents.
- A city may mostly belong to one Senate District, but a small portion of its residents could be in another.
These overlaps can have real implications for representation, funding decisions, and policy impacts at both local and state levels. They can also shape future political opportunities. If a city overlaps only marginally with an Assembly District, a councilmember from that city may have a smaller built-in base of support if they run for that higher office—compared to another candidate whose city covers a larger portion of the same district.
The overlap tables display:
- % of [This Jurisdiction]: The percentage of this jurisdiction’s population that belongs to the overlapping district.
- % of [Other District]: The percentage of the other district’s population that resides within this jurisdiction.
This provides a simple way to see, at a glance, how populations are shared across district boundaries.