How IP3 ASSESS Handles Trendlines Across Changing Census Tract Boundaries

IP3 ASSESS uses 2020 census tract boundaries as the standard for all visualizations, even when data spans multiple years. To ensure consistent trendlines over time, we convert all data points to align with 2020 tracts using the following method:

• Tract Splits: When one tract from an earlier year (e.g., 2010) splits into multiple 2020 tracts, the original data is duplicated across the resulting tracts.
• Tract Joins: When multiple earlier tracts merge into a single 2020 tract, IP3 ASSESS uses weighted calculations based on the percentage of overlap between the old and new boundaries. We apply a weighted mean aggregation for demographic and similar data that considers both tract overlap and any denominator values (such as population counts) from the original data.