Hello Tim,

The goal of PSAP is to produce meaningful statistical geographies for data users while maintaining consistent statistical geography nationwide.

The Census Bureau classifies two types of geographies: legal and statistical geography.

Statistical geographies are areas defined solely for data collection, tabulation, dissemination, and analysis. That said, we recognize that statistical geographies—census tracts, especially—are used in a variety of federal programs. Though it is tempting to want to change boundaries to meet the needs of a particular program, please be aware that a change that may have a positive effect for one program may have a negative impact on another. It is better to maintain the statistical objectivity and comparability of areas, updating areas to meet the general analytical needs of as many data users as possible.

Statistical Geography boundaries generally follow permanent, visible features that are identifiable in the field.

Boundaries should:

• Follow visible features whenever possible.

• Use significant/major features on landscape.
• Align to legal geography where a relationship has been established and is unlikely to change over the decade due to changes in the legal entity’s boundary.
• Follow legal conjoint boundaries, where applicable. For example, given the stability of city and town boundaries in the Northeast, census tract boundaries may align with the boundaries of a city or town. With census designated places, it is preferable to align with a city boundary than to leave a small gap between the two places.
• Reflect current land use patterns where possible.

Boundaries should not:

• Cut through housing and other buildings.
• Include “zig-zags” and sharp angles for no purpose.
• Group disparate land use types for no reason.
• Make use of less prominent features when a more significant feature could be used.

The following criteria apply to census tracts in the United States, Puerto Rico, and the Island Areas:

• Census tracts must not cross county or state boundaries.

• Census tracts must cover the entire land and water area of a county.

• Census tracts must comprise a reasonably compact and contiguous land area, with a few exceptions.

• Exceptions to the compactness requirement might include areas with unique population groups, land uses, or settlement patterns, such as coastal communities, a community ringing a lakeshore, valley settlements, and commercial and industrial development along a linear transportation route defined as a special use census tract.

• Census tract boundaries should follow visible and identifiable features.

• Census tracts must have a basic numeric identifier composed of no more than four digits and may have a two-digit decimal suffix.

The Census Bureau may modify and, if necessary, reject any proposals for census tracts that do not meet the published criteria.

In addition, the Census Bureau reserves the right to modify the boundaries and attributes of census tracts as needed to meet the published criteria and/or maintain geographic relationships before or after the final tabulation geography is set for the 2020 Census.

Census tracts must meet specific population and housing unit thresholds outlined on the next slide Census Tract Thresholds.