DOI: 10.57761/v1mj-g071
title: Cotality Smart Data Platform: Historical Property

description: If you have questions or concerns, please contact Ron Nakao at ronbo@stanford.edu.
description: Title: Cotality Smart Data Platform (SDP): Historical Property

Historical tax assessment data for all U.S. states, the U.S. Virgin Islands, Guam, and Washington, D.C. Each table represents a previous edition of Cotality's tax assessment data.

Formerly known as CoreLogic Smart Data Platform: Historical Property.
description: 



In the United States, parcel data is public record information that describes a division of land (also referred to as "property" or "real estate"). Each parcel is given a unique identifier called an Assessor’s Parcel Number or APN. The two principal types of records maintained by county government agencies for each parcel of land are deed and property tax records. When a real estate transaction takes place (e.g. a change in ownership), a property deed must be signed by both the buyer and seller. The deed will then be filed with the County Recorder’s offices, sometimes called the County Clerk-Recorder or other similar title. Property tax records are maintained by County Tax Assessor’s offices; they show the amount of taxes assessed on a parcel and include a detailed description of any structures or buildings on the parcel, including year built, square footages, building type, amenities like a pool, etc. There is not a uniform format for storing parcel data across the thousands of counties and county equivalents in the U.S.; laws and regulations governing real estate/property sales vary by state. Counties and county equivalents also have inconsistent approaches to archiving historical parcel data.



To fill researchers’ needs for uniform parcel data, Cotality collects, cleans, and normalizes public records that they collect from U.S. County Assessor and Recorder offices. Cotality augments this data with information gathered from other public and non-public sources (e.g., loan issuers, real estate agents, landlords, etc.). The Stanford Libraries has purchased bulk extracts from Cotality's parcel data, including mortgage, owner transfer, pre-foreclosure, and historical and contemporary tax assessment data. Data is bundled into pipe-delimited text files, which are uploaded to Data Farm (Redivis) for preview, extraction and analysis.



For more information about how the data was prepared for Redivis, please see [Cotality 2024 GitLab](<https://code.stanford.edu/sul-cidr/cotality-2024/>).






description: Each table contains an archived snapshot of the property data, roughly corresponding to the following assessed years:



- Historical Property 1 = 2022-2023
- Historical Property 2 = 2021-2022
- Historical Property 3 = 2020-2021
- Historical Property 4 = 2019-2020
- Historical Property 5 = 2018-2019
- Historical Property 6 = 2017-2018
- Historical Property 7 = 2016-2017
- Historical Property 8 = 2015-2016
- Historical Property 9 = 2014-2015
- Historical Property 10 = 2013-2014
- Historical Property 11 = 2012-2013
- Historical Property 12 = 2011-2012
- Historical Property 13 = 2010-2011
- Historical Property 14 = 2009-2010
- Historical Property 15 = 2008-2009

<!-- -->



Users can check the`ASSESSED_YEAR` variable to confirm the year of assessment.



Roughly speaking, the tables use the following census geographies:



- 2020 Census Tract: Historical Property 1-2
- 2010 Census Tract: Historical Property 3 – 12
- 2000 Census Tract: Historical Property 13 – 15

<!-- -->



The Property, Mortgage, Owner Transfer, Historical Property and Pre-Foreclosure data can be linked on the `CLIP`, a unique identification number assigned to each property.



For more information about included variables, please see **cotality\_sdp\_historical\_property\_data\_dictionary\_2024.txt **and **Historical Property\_v3.xlsx.**



Under **Supporting files**, users can also find record counts per FIPS code for each edition of the Historical Property data.



For more information about how the Cotality Smart Data Platform: Historical Property data compares to legacy data, please see **2025\_Legacy\_Content\_Mapping.pdf*****.***