Adjusted Weighted Repeat Sales Index for Disaggregated Real Estate Valuation

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Solution Overview

Problem

The weighted repeat sales index (WRSI) struggles to accurately estimate real estate growth rates at disaggregated geographic levels, such as zip codes or census tracts, due to fewer transactions, leading to lagged and non-seasonal property value assessments.

Innovation Solution

An adjusted WRSI method that calculates deviations from aggregated levels to disaggregated levels using a repeat sales house price index function, incorporating data from aggregated levels to improve forecasting accuracy and detect seasonal trends at lower geographic levels.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the WRSI uses data from disaggregated geographic levels (zip codes, census tracts), then the localization precision is improved, but the quantity of transactions is reduced leading to lagged and non-seasonal property value assessments

Engineering Contradiction:
Improvelocalization precisionVSAvoidquantity of transactions
Core Design Contradiction:
Measurement precisionVSQuantity of substance

Solution Approach 1:

The patent combines data from multiple geographic levels (aggregated and disaggregated) to create a hybrid index. The adjusted WRSI merges the localized precision of disaggregated data with the statistical reliability of aggregated data, allowing the system to maintain high localization precision while compensating for insufficient transaction quantities at the disaggregated level through borrowing strength from higher aggregation levels.

Inventive Principle:
Principle #5Merging (Combining)

2Measurement precision

If the WRSI focuses on disaggregated levels to improve market condition analysis, then the measurement precision is improved, but the reliability is reduced due to fewer transactions

Engineering Contradiction:
Improvemarket condition analysis accuracyVSAvoidassessment reliability
Core Design Contradiction:
Measurement precisionVSReliability

Solution Approach 1:

The patent applies local quality by allowing different geographic levels to have different weights and characteristics in the index calculation. Disaggregated levels receive higher weight for localization precision where sufficient transactions exist, while aggregated levels provide reliability support where transaction data is sparse. This creates a spatially varying quality structure that optimizes both precision and reliability locally.

Inventive Principle:
Principle #3Local quality

3Measurement precision

If the WRSI uses only disaggregated level data to detect seasonal trends, then the measurement precision is improved, but the loss of time increases due to lagged assessments

Engineering Contradiction:
Improvetrend detection precisionVSAvoidassessment timeliness
Core Design Contradiction:
Measurement precisionVSLoss of time

Solution Approach 1:

The patent performs preliminary action by using aggregated level data to establish early trends and seasonal patterns that can be detected sooner due to larger transaction volumes. These preliminary findings from aggregated levels serve as leading indicators that prepare the system to quickly interpret and validate patterns when disaggregated data becomes available, reducing the overall time loss in trend detection.

Inventive Principle:
Principle #10Preliminary action

Data Source

PatentUS10453155B1System and method for providing an adjusted weighted repeat sale index
Publication Date: 2019.10.22 FREDDIE MAC
  • US10453155B1 patent drawing
  • US10453155B1 patent drawing
  • US10453155B1 patent drawing

AI summary

Systems, methods, and computer-readable storage media are described for estimating real estate property values based on an adjusted repeat sales model. In one exemplary embodiment, a computer-implemented method comprises calculating data for estimating the adjustments from aggregated levels to disaggregated levels by marking a first transaction to a second transaction using a repeat sales house price index function at an aggregated level; determining, using the calculated data, an estimate of the deviation between the repeat sales house price index at the aggregated level and a repeat sales house price index at a disaggregated level; and calculating the repeat sales house price index at the disaggregated level based on the determined estimate of the deviation from the aggregated level.