The U.S. Census Bureau publishes updated boundary files every year. The most consequential years are those that fall on the decennial Census: 2000, 2010, 2020. For at least the last 70 years Census Tract boundaries have fallen within the city’s municipal boundary until Census 2020. Census tracts are typically drawn to include between 1,200 to 8,000 people with the optimal goal being around 4,000 people. Census tracts are often used as a default “neighborhood” level of analysis.

The new Census tract boundaries include a handful of oddities that for the most part contribute no change to the Census data reporting. Three boundary changes now extend beyond the city boundary, but add no people to be counted in those extension areas.

It is unclear why the Census decided to expand Census tract boundaries beyond the city boundary when it doesn’t change or improve data collection or reporting and instead opens the opportunity to make data reporting more confusing for Michigan’s largest city.