Why is the data different?

ATTOM often gets queries from customers seeking to understand why they sometimes get different data from different sources.

Source Issues

One of the key philosophies behind the ATTOM Cloud platform is to draw data from a single consistent source. In almost all cases, the data provided in ATTOM API comes from the same database used by ATTOM Cloud. This reduces differences but does not eliminate the,. For example, we collect data about the ownership of a property from many sources. It can come from the county Tax Assessor, the county Recorder, and on filings for Building Permits. The information provided by the county Recorder can include deed documents changing ownership, and mortgages which do not agree. This can lead to different names being provided. The number of bedrooms for a property is sourced from data provided by the county Tax Assessor and can be included in listing data when a property is sold. When the data from sources differ, it can be challenging to establish which is the most accurate.

Timing Issues

At best, property data represents a snapshot in time. Over many years a property can be subdivided into multiple properties, multiple properties can be consolidated into a single property, a single property can be torn down and rebuilt, undergo significant improvements, change ownership, and even be moved into new school districts or census blocks. These all have the potential to significantly change the attributes of a property and how we record history. ATTOM sources property data from many sources. The data collected from each source can be for differing points in time, leading to differences in the data reported.

Coverage Issues

Because property data is collected from many jurisdictions it is not always possible to get consistent data for every jurisdiction. In fact, there are some jurisdictions where no data is available at all. One county might choose to track the presence and size of the swimming pool on a property and a neighboring county may not. An incorporated city might require building permits to be issued for all properties in the city, whereas properties outside the city limits but forming part of the same postal city may not. This can result in apparent inconsistencies in the data reported. ATTOM published coverage reports, field population reports, and field density reports to outline these differences at a county level. A separate analysis of the data may be required to uncover gaps in the coverage.

Naming Issues

Properties are grouped into areas using various boundaries. Sometimes, the same name can be used for different boundary (geography) types.

Example

Waterloo is an incorporated city (Place) in Iowa. It is defined by the area shown in yellow (below). USPS services in that area are based upon a separate definition for the Postal City of Waterloo (Oblue). This is made up of three zip codes (50701, 50702, and 50703). Small parts of the city fall in other zip codes e.g. part of Waterloo incorporated city fall into the postal city of Cedar Falls. As can be seen on the map, these zip codes, and hence the postal city, extend well beyond the boundaries of the incorporated city. The Census Bureau defines Zip Code Tabulation AAreas (ZCTA) for each of these zip codes, in which it assigns Census Blocks. This results in a third definition of Waterloo. Waterloo has three separate definitions

Legal - Incorporated city boundary
Postal - Postal City (accumulation of zip codes)
Economic/Census - Aggregation of properties in Census Blocks into Zip Code Tabulation Areas

The following SQL query establishes the area, population, and number of households in Waterloo incorporated city (Place).

Select 
	dp.LandAreaSquareMiles,
	com.Population_2010,
	com.Households 
	
From adw.DimPlace dp 
Left join adw.Community com on dp.PlaceGeoID = com.GeoID 

Where dp.Name = 'Waterloo' And dp.PlaceFipsCode = 82425

Area: 61.49
Population: 68,158
Households: 29,276

The following query establishes the area, population, and number of households in Waterloo postal city.

Select 
	dp.AreaSquareMiles,
	com.Population_2010,
	com.Households 
	
From adw.DimPOstalCity dp 
Left join adw.Community com on dp.PostalCityGeoID = com.GeoID 

Where dp.Name = 'Waterloo' And dp.CountyKey = 36426

Area: 182.33
Population: 69,158
Households: 29,793

The following REST call could be used to identify the geocode for the incorporated city of Waterloo, IA. The county name is provided because place names are not always unique within a state.

https://api.gateway.attomdata.com/v4/location/lookup?name=Waterloo%2C%20Black%20Hawk%20County%2C%20IA&geographyTypeAbbreviation=PL

The following REST call could be used to identify the geocode for the postal city of Waterloo, IA

https://api.gateway.attomdata.com/v4/location/lookup?name=Waterloo%2C%20IA&geographyTypeAbbreviation=CI

The geocode (geoIdV4) can then be used to return area data such as crime statistics, demographics, or sales trends