Wednesday, July 10, 2024

The Power of Three: Analyzing Comparables with Least Adjustment, Sales Recency, and Geographic Proximity (Part 3 of 3)

Target Audience: New Graduates/Analysts 

Introduction

Analysts and appraisers often use comparable sales analysis to determine a property's value. However, there are various methods within comparable sales analysis, each with advantages and limitations. This blog post will explore three primary comparable-based valuation methodologies: Least Adjustment, Sales Recency, and Geographic Proximity. We aim to showcase the nuances of each approach by using the same statistically derived adjustment matrix and analyzing 20 comparable sales, providing valuable insights for analysts and appraisers navigating the world of property valuation based on comparable sales.

1. Least Adjustment Method

(Click on the image to enlarge)

Dataset and Variables

A regression analysis using home sales data from a specific town from January 2023 to June 2024 helped generate coefficients for an adjustment matrix to value a series of subject properties with a valuation date of July 1, 2024.

One of the variables used in the analysis is "Months Since," representing the number of months since the sale took place. For example, a sale in January 2023 received a value of 18 (July 2024 minus January 2023), while a sale in June 2024 received 1.

The table illustrates adjustments for 20 comparable sales that were used to value the subject property with the following characteristics:

- Land SF=6,534

- Bldg Age=8

- Heated SF=1,914

- Baths=2.5

- Exterior Wall=Hardiboard.

The adjustment coefficients used are as follows:

- Months Since=217.11

- Land SF=2.08

- Bldg Age=-264

- Heated SF=145.40

- Baths=33,301

No adjustment was applied for the exterior wall, as all comparables have the same Hardiboard exterior wall as the subject property. While the "Months Since" variable provided the time adjustment for the comps, no location adjustment was used as all 20 comparables were chosen from the same neighborhood as the subject property.

Since the "least" adjustment comparables methodology was used in this solution, the adjustments were absolute, so an adjustment of +20,000 was treated the same as one with -20,000. Out of the 20 comparables, the average of the 10 comps requiring the least adjustments contributed to the subject's value conclusion.

Analysis

This comparables analysis involves adjusting the sale prices of 20 comparable properties to determine the value of a subject property with specific characteristics. The adjustments are made based on various property attributes such as Land SF, Building Age, Heated SF, Baths, and Months Since (the sale took place) and an adjustment for the Exterior Wall material.

1.    Adjustment Methodology:

  • Using the "least adjustment" methodology, the 10 comparables requiring the least adjustments contributed to the subject property's value conclusion. This method aims to find the most similar properties to the subject by minimizing the adjustments needed.
  • The adjustments made were absolute, meaning that the direction of the adjustment (positive or negative) did not impact the calculation. This approach simplifies the analysis and ensures that adjustments are treated uniformly regardless of the direction of change.

2.    Specific Adjustments:

  • The adjustments were determined based on the coefficients derived from a regression analysis. The adjustments for each variable (Land SF, Building Age, Heated SF, and Baths) were specific values that were added or subtracted from the sale prices of the comparables.
  • The adjustment for "Months Since" was calculated as 217.11 times the number of months since the sale occurred. This adjustment factor reflects the temporal aspect of the sales data and helps account for changes in property values over time.

3.    Average of 10 Least-adjusted Comps:

  • The average sale price of the 10 comparables with the least adjustments was used to estimate the subject property's value. This approach prioritizes properties most similar to the subject in terms of their characteristics, leading to a more accurate value estimate.
  • The average of the 10 least-adjusted comparables was calculated to be $439,664, which serves as the basis for the subject property valuation.

In conclusion, this comparables analysis utilized a systematic approach to adjust the sale prices of comparable properties based on specific property characteristics and time-related factors. By applying the least adjustment methodology and using absolute adjustments, the analysis aimed to provide a reliable estimate of the subject property's value while minimizing the impact of outliers and errors in the data.

Important to Know (for New Analysts)

The use of absolute adjustments is appropriate in the "least adjustment" methodology in the comparables analysis.

When employing the "least adjustment" approach, the main goal is to identify the most comparable properties to the subject property by minimizing the adjustments needed to align the characteristics of the comparables with those of the subject. This methodology focuses on selecting properties that require the least adjustment to match the subject property's features, thereby reducing the potential for introducing bias or error into the valuation process.

By using absolute adjustments, where the direction of the adjustment (positive or negative) does not affect the calculation, the analysis ensures a consistent and standardized treatment of the adjustments applied to the comparable properties. This approach allows for a more precise comparison between properties and simplifies the valuation process by considering the magnitude of the adjustment rather than the direction of change.

Therefore, in the specific context of the "least adjustment" method for comparables analysis, the use of absolute adjustments is appropriate and aligns with the goal of selecting the most similar properties to the subject property while maintaining consistency and minimizing potential biases.

2. Sales Recency Method


Analysis

Again, out of the same 20 comparables, the average of the ten most recent comps contributed to the subject's value conclusion.

Using signed adjustments (positive or negative) in the "sales recency" methodology is significant as it allows for a more precise valuation by considering the direction and magnitude of the adjustments. For instance, positive adjustments indicate that a comparable property was superior in certain aspects compared to the subject property, while negative adjustments signify inferiority.

In this case, the adjustments for each comparable have been calculated based on the specific characteristics of the subject property and the comparables, with adjustments reflecting how each property differs in terms of Land SF, Building Age, Heated SF, Baths, and the recency of the sale. This approach enables a more nuanced valuation considering the similarities and differences between the subject property and the comparables.

The prioritization of more recent sales in the valuation process, as indicated by the emphasis on the "Months Since" variable, aligns with the principle of sales recency methodology. Focusing on recent sales, this methodology captures current market conditions and trends more accurately, providing a more relevant basis for valuing the subject property.

Moreover, the average of the ten most recent adjusted comps contributing to the subject's value conclusion ensures that the valuation reflects the most up-to-date market data, given the preference for recent sales in the analysis. This approach helps mitigate the impact of potentially outdated or less relevant data from older sales, leading to a more accurate valuation of the subject property.

Overall, the detailed analysis and use of signed adjustments in this comparable solution demonstrate a thorough and systematic approach to property valuation. This approach considers the specific characteristics of each property and prioritizes recent sales data to arrive at a reliable estimation of the subject property's value.

Important to Know (for New Analysts)

Using signed adjustments in the "sales recency" comparable method is appropriate.

This method considers the recency of sales to prioritize more recent transactions over older ones in the valuation process. By applying signed adjustments that reflect the direction and magnitude of the differences between the subject property and the comparables, the analysis more effectively accounts for the variations in property characteristics and market conditions.

In contrast, the least adjustment method typically involves absolute adjustments that do not differentiate between whether a property is superior or inferior to the subject property in a particular aspect.

Therefore, by using signed adjustments, the sales recency comparable solution can better reflect each comparable property's relative strengths and weaknesses compared to the subject property. This leads to a more insightful and reliable valuation result that considers the most recent market trends and conditions while considering each property's specific characteristics in the analysis.

3. Geographic Proximity Method


The "geographic proximity" comparable method utilizes the comparables based on their physical proximity to the subject property. This method assumes that properties close to the subject are more likely to have similar characteristics, thus providing a more accurate valuation.

This methodology used ten comparables, instead of 20, from the same dataset. Out of the ten comparables, the average of the five comps geographically closest to the subject contributed to the value conclusion.

In this case, the signed adjustments (positive or negative) are applied to each comparable sale to reflect how its specific features differ from those of the subject property. These adjustments are necessary to ensure that the comparable sales are brought in line with the subject property, accounting for differences in variables such as Land SF, Building Age, Heated SF, and Baths.

Using signed adjustments allows for a more nuanced comparison of the comparables to the subject property. By applying adjustments to account for specific differences in characteristics, the final adjusted sale prices are more reflective of the subject property's market value. This approach is particularly beneficial when valuing properties in a homogeneous neighborhood with similar characteristics.

Overall, the analysis confirms that the use of signed adjustments in the geographic proximity methodology is appropriate for valuing the subject property and ensures a more accurate valuation based on the specific characteristics of the comparable properties.

Important to Know (for New Analysts)

Including a map showing the proximity of the comparables selected based on the geographic proximity methodology is customary and highly beneficial in the valuation process. By providing a visual representation of the locations of the comparable sales in relation to the subject property, the map offers crucial context and transparency to the analysis.

The map helps in understanding the physical proximity of the comparables to the subject property, reinforcing the rationale behind selecting these specific properties for comparison. It also allows for a quick and intuitive visualization of how the selected comps are distributed geographically, which can aid in assessing the reliability of the comparables and the validity of the geographic proximity methodology.

Furthermore, the map can be valuable during discussions or presentations, providing a clear visual reference that complements the numerical data and adjustment grid. It can help stakeholders, such as clients or appraisal reviewers, to grasp the geographic context of the comparables and the subject property more effectively.

Pros and Cons of each Methodology

Each of the three primary comps selection methodologies – Least Adjustment, Sales recency, and Geographic Proximity – has its own set of advantages and disadvantages. Here are the pros and cons of each methodology:

1.    Least Adjustment Methodology:

·          Pros:

 o   Easy to understand and apply: This method involves selecting comparable properties that require the least amount of adjustment to align with the subject property.

 o   Can be useful in neighborhoods with diverse properties: In areas with a wide range of property types, this method may help identify the most comparable sales.

·          Cons:

o   Ignores property characteristics: This approach focuses primarily on minimizing adjustments, which may lead to overlooking key differences in property features and conditions.

o   May not account for market trends: Does not consider how recent sales or geographic proximity may impact the subject property's market value.

2.    Sales Recency Methodology:

 Pros:

o   Reflects current market conditions: It prefers more recent sales, which may better reflect current market trends and conditions.

o   Provides insight into market changes: By focusing on recent sales, this method can offer a glimpse into how property values have evolved over time.

  Cons:

     o   Limited historical data: Prioritizing recency may result in fewer comparable sales to choose from, especially in slower market conditions.

     o   May not capture long-term trends: Relying solely on recent sales could overlook longer-term market trends that impact property values.

3.    Geographic Proximity Methodology:

 Pros:

o   Considers localized trends: Selecting comparables based on geographic proximity can provide insights into specific neighborhood dynamics and market conditions.

o   Aligns with market segmentation: Recognizes that properties in close physical proximity are more likely to have similar characteristics and values.

  Cons:

o   Limited comparables selection: Depending on the neighborhood size or property availability, the pool of comparable sales may be restricted.

o   Ignores property uniqueness: Emphasizing geographic proximity may overlook unique features contributing to a property's value.

In conclusion, each comps selection methodology has its own strengths and limitations. The choice of methodology should be guided by the specific characteristics of the subject property, the available data, and the local market conditions. Combining elements of multiple methodologies or customizing the approach based on the property's unique attributes can often lead to a more robust and accurate valuation.

Averaging the Three Values

In comparable sales analysis, it is generally not recommended to average the results of different valuation methodologies, even when the values are not significantly far apart. Each valuation method has its assumptions, strengths, and limitations, and combining them in such a way may not provide a comprehensive or accurate representation of the subject property's value.

The three comparable sales-based valuation methodologies involve distinct approaches and considerations in determining property values. By averaging the values derived from these methodologies, one risks diluting each method's specific insights and adjustments, potentially leading to a less precise and reliable overall valuation.

Instead, it is advisable to critically evaluate the results of each valuation methodology based on their merits, the underlying assumptions, and the specific characteristics of the subject property, considering factors such as the quality and relevance of the comparables selected, the appropriateness of the adjustment matrices used, and the rationale behind the adjustments applied.

If the values produced by the different methodologies are not significantly divergent, it may be more appropriate to carefully review the methodology that best aligns with the subject property's characteristics and market conditions. This approach ensures that the final value conclusion is based on a solid foundation supported by a thorough and methodologically sound analysis.

In summary, while multiple valuation methodologies and viewpoints must be considered in the valuation process, it is generally recommended that the most appropriate and robust methodology be used to determine the subject property's value rather than averaging different methods.

Series Conclusion

This three-part series has explored a novel approach to comparable sales analysis for valuing single-family homes. We began by leveraging a correlation matrix to uncover potential biases and multicollinearity among key property features. This data-driven foundation ensured a more robust regression model, ultimately generating an adjustment matrix. This matrix provided a systematic and objective way to account for property-specific differences within the comparable data set.

We have unlocked a more informed valuation conclusion by integrating statistical analysis with traditional comparable sales analysis. Applying the adjustment matrix alongside classic valuation methodologies like Least Adjustment, Sales Recency, and Geographic Proximity has significantly reduced the subjectivity inherent in traditional adjustments. This approach leads to greater consistency and reliability and enhances the accuracy of property valuations, a significant benefit for real estate professionals.

This series has presented a more robust and objective comparable sales methodology framework. My upcoming book will delve even deeper, exploring the application of this methodology to a broader range of property types and geographical scales, which includes county-level valuations with town-specific adjustments and applications for valuing townhouses, condominiums, Planned Unit Developments (PUDs), Planned Unit Developments (MPUDs), and more. By expanding the scope of analysis, this book will aim to empower analysts and appraisers with a powerful new tool for generating accurate and defensible property valuations across a broader spectrum of the real estate market.

Sid's Bookshelf: Elevate Your Personal and Business Potential

Wednesday, July 3, 2024

The Art and Science of Comparable Sales Analysis (Part 2 of 3)

Target Audience: New Graduates/Analysts

Using a regression-based adjustment matrix in comparable sales analysis is a common and sound practice in real estate valuation. Regression analysis can provide insights into the factors that influence property values by analyzing the relationship between the sale price of properties and various independent variables. It allows for the creation of an adjustment matrix with uniform coefficients to adjust comparable sales to the subject properties, ultimately leading to more accurate valuations.

Dataset and Variables

This regression output was developed using home sales dataset from a specific town for eighteen months, from January 2023 to June 2024, generating coefficients to help create a statistically significant adjustment matrix with uniform coefficients, aiding in adjusting the comparables to evaluate a series of subject properties with a targeted July 1, 2024 valuation date.

The regression analysis uses the sale price as the dependent variable and six independent variables. One of the variables, "Months Since," represents the number of months since the sale took place. For example, a sale in January 2023 will be assigned a value of 18 (July 2024 minus January 2023), while a sale in June 2024 will be given a value of 1. By applying the coefficient value to the months, sales from January 2023 will receive an upward adjustment of $3,908 ($217.11 multiplied by 18), and sales from June 2024 will be adjusted by $217.11 ($217.11 multiplied by 1).

The "Exterior Wall" variable has been effect-coded to focus on the deviation of each category from the town's median sale price. The effect-coded Exterior Wall values range between +$93,100 (Stone) and -$30,000 (Concrete Block).

Bldg Age is a synthetic variable calculated by subtracting the year the property was built from the prediction year 2024. The other variables are quantitative data variables obtained from public records.

Since all properties and comparables will come from specific neighborhoods within this town, no location variable has been introduced. Finally, the intercept was forced to zero, as this regression was conducted to produce coefficients to adjust comparables externally rather than producing competing regression values, per se.

Analysis

Now, let's analyze the regression output:

1. Multiple R and R Square: Multiple R of 0.981996 indicates a strong positive relationship between the independent variables and the dependent variable (sale price). The R Square value of 0.964316 suggests that approximately 96.43% of the variance in the dependent variable can be explained by the independent variables in the model.

2. ANOVA: The ANOVA table shows that the regression model is statistically significant. The F-statistic of 4,400.37 with a p-value of 0 indicates that the regression model as a whole is a good fit for the data.

3. Coefficients:

o    The coefficient for "Months Since" is 217.11, implying that for each additional month since the sale, the sale price increases by $217.11.

o    The coefficient for "Land SF" is 2.08, indicating that for every additional square foot of land, the sale price increases by $2.08.

o    The negative coefficient for "Bldg Age" (-263.638) signifies that as the age of the building increases, the sale price decreases by $263.638.

o    Heated SF: An increase of 1 unit in Heated SF leads to an increase of $145.43 in sale price.

o    Bathroom: Each additional bathroom is associated with an increase of $33,300.96 in sale price.

o    Exterior Wall: The effect-coded variable indicates how the specific type of exterior wall affects the sale price.

Overall, the regression output suggests that the model with these independent variables can explain a substantial portion of the variation in sale prices. The coefficients provide insights into the relationships between the independent variables and the sale price, which can be used to adjust comparable sales for more accurate valuations. This approach provides a data-driven method for ensuring fair and accurate valuations using comparable sales analysis.

It's important to note that the soundness of the experiment also depends on the quality and representativeness of the data used, the appropriateness of the variables selected, and the assumptions made in the regression analysis. Conducting further validation and sensitivity analyses can help ensure the reliability of the regression-based adjustment matrix for property valuations.

Important to Know (for New Analysts)

1. Months Since variable

Given that "Months Since" has passed the multicollinearity test (discussed in Blog Post 1) and the importance of its explainability, here is why you might consider keeping the variable in the model despite its weak p-value:

Multicollinearity is not a concern: Since "Months Since" doesn't correlate highly with other independent variables, it provides unique information about the time-based adjustments, strengthening the argument for keeping it in the model.

Explainability is crucial: If reviewers and taxpayers need to understand the rationale behind the adjustments, "Months Since" explains why older sales receive higher adjustments to account for market changes.

Here are some strategies to address the weak p-value:

Explaining the context: It must be clearly stated in the report that "Months Since" is included for explanatory purposes, even though its p-value is not statistically significant at the usual 0.05 level, additionally mentioning that it passed the multicollinearity test and emphasizing its role in improving model interpretability.

Focusing on coefficient direction and magnitude: While the p-value suggests a lack of strong statistical evidence, it's wise to discuss the positive coefficient of "Months Since" and its implication that older sales receive larger adjustments, aligning with market trends where recent sales likely reflect more current prices.

Exploring alternative presentations: It's worth presenting the adjustment matrix alongside a graph that visually depicts the impact of "Months Since" on the adjustment, providing a clearer picture of the time-based adjustments.

Overall, retaining “Months Since” seems reasonable in this case. The lack of multicollinearity and the importance of explainability outweigh the concern about the p-value. However, it's crucial to ensure clear communication regarding the variable's limitations in terms of statistical significance, maintaining transparency and trust in the analysis.

Forcing the Intercept to Zero

Forcing the intercept term to zero in a regression model is common in some contexts, especially when the focus is on estimating coefficients for adjustment purposes rather than predicting absolute values. In this case, the regression was conducted to produce coefficients to adjust comparable sales externally, not to predict the actual sale prices of properties.

Statistically, forcing the intercept to zero can be sound if there is strong support from the underlying theory or domain knowledge. This suggests that the relationship between the independent variables and the dependent variable passes through the origin (i.e., when all independent variables equal zero, the dependent variable should also equal zero).

Since the regression was explicitly conducted to produce coefficients for adjustment purposes rather than predicting absolute values, forcing the intercept to zero is justifiable. However, it's essential to ensure that the statistical soundness of this decision aligns with the specific requirements and goals of the analysis. Conducting sensitivity analyses or comparing the results with and without the intercept term forced to zero could provide further insights into the robustness of the regression model.

Regression-based Adjustment Matrix

Important to Know (for New Graduates)

When performing a comparable sales analysis, adjustments are typically made to the sale prices of the comparable properties to account for differences in their characteristics relative to the subject property. The idea is to estimate how much the comparable properties would have sold for if they had the exact same characteristics as the subject property.

In this context, since the subject property serves as the baseline or reference point against which adjustments are made, no adjustment needs to be applied directly to the subject property itself. Instead, adjustments are calculated for each comparable property based on the differences in their characteristics compared to the subject property. These adjustments are then applied to the sale prices of the comparable properties to arrive at adjusted sale prices that reflect the value of the comparables as if they were similar to the subject property.

Therefore, in the absence of a sale price for the subject property, the focus is on adjusting the sale prices of the comparable properties relative to the subject property to estimate the subject's value accurately.

Here is a comprehensive analysis of the adjustment process:

1. Sale Month Adjustment:

  • The adjustment for the month of sale is made based on the difference in months between the sale date of the comparables and the valuation date (July 2024). A higher number of months since the sale leads to a more significant adjustment.
  • For example, Comp-1 was sold in January 2023, 18 months before the valuation date. The adjustment for Comp-1 is calculated as 18 * 217.11 = 3,908.
  • The adjustment for Comp-2 is smaller as it was sold in June 2024, just one month before the valuation date. The adjustment for Comp-2 is 1 * 217.11 = 217.
  • These adjustments account for the time difference in property sales.

2. Land SF Adjustment:

  • The adjustment for Land Square Footage is based on the differences between the subject and comparable properties. A larger size receives a negative adjustment, while a smaller size receives a positive adjustment.
  • For example, Comp-1 has 11,000 SF, and the subject has 10,454 SF. The resulting negative adjustment for Comp-1 is (10,454 - 11,000) * 2.08 = -$1,136.
  • Similarly, the adjustment for Comp-2 is positive as it has 9,000 SF, resulting in an adjustment of (10,454 - 9,000) * 2.08 = $3,024.

3. Bldg Age Adjustment:

  • The adjustment for Building Age is based on the age of the buildings relative to the subject property. Older properties receive a negative adjustment, while newer ones receive a positive adjustment.
  • For example, Comp-1 is 40 years old, while the subject is 47. The adjustment for Comp-1 is (47 - 40) * -263.64 = $1,845.
  • On the other hand, Comp-2 is 55 years old, resulting in an adjustment of (47 - 55) * -263.64 = -$2,109.

4. Heated SF Adjustment:

  • The adjustment for Heated Square Footage is made with the same objectivity as the Land SF adjustment. Larger sizes receive negative adjustments, and smaller sizes receive positive adjustments. For example, Comp-1 has 1,750 SF, while the subject has 1,664 SF. The adjustment for Comp-1 is (1,664 - 1,750) * 145.43 =—$12,507.
  • In contrast, Comp-2 has 1,550 SF, leading to an adjustment of (1,664 - 1,550) * 145.43 = $16,579.

5. Bathrooms Adjustment:

  • The coefficient for Bathrooms is 33,300.96.
  • The adjustment for Bathrooms is calculated as the difference between the number of bathrooms in each comparable property and the subject property, multiplied by the coefficient.
  • Comp-1 has three bathrooms, while the subject property has two bathrooms.
  • The adjustment for Comp-1 is (3 - 2) * 33,300.96 = -$33,300.96.
  • Similarly, the adjustment for Comp-2 can be calculated based on the number of bathrooms in Comp-2 relative to the subject property.

6. Exterior Wall Adjustment:

·   Given that the subject property's Exterior Wall is Stone, we can calculate the adjustments for the Exterior Wall for the comparable properties using the effect-coded values. Here is how the adjustments for the Exterior Walls for Comp-1 and Comp-2 can be calculated based on the effect-coded values:

  • For Comp-1 with an exterior wall of Concrete Block (effect-coded value is -$30,000): Adjustment = (-$30,000 - $93,100) * 0.16 = -$10,096.
  • For Comp-2 with an exterior wall of Stone: Adjustment = ($93,100 - $93,100) * 0.16 = $0.

7. Total Adjustments and Adjusted Sale Price:

  • By summing up all the individual adjustments for each comparable property, we arrive at the total adjustments made to adjust the comparable sale prices to reflect the subject property's characteristics.
  • The adjusted sale price for each comparable property is obtained by adding the total adjustments to the original sale price.
  • The subject value is then calculated as the average of the two adjusted sale prices.

In essence, the adjustment process involves:

  • Carefully analyzing the differences in characteristics between the subject property and the comparables.
  • Applying the respective coefficients to make adjustments.
  • Arriving at an adjusted sale price for each comparable property.

The subject value is then determined based on the average of the adjusted sale prices.

Conclusion

In this blog post, I used multiple regression analysis to show how statistically sound coefficients can help adjust comparable sales and accurately value subject properties. The regression output provided clear evidence of the impact of these coefficients in the valuation process, leading to more refined and reliable estimates. While the study focused on a specific town with limited adjustment variables, the upcoming book will explore more advanced analyses across various counties, covering the development and application of regression-based adjustment matrices at the county and tax district levels, including techniques such as hybrid fixed neighborhood and location surface analysis, effect-coded categorical variables, one-hot binary variables, and more. These advancements will undoubtedly improve the precision and sophistication of property valuation methodologies, setting a new standard in the field.

Coming Soon: Part 3 of 3 – Applying regression to value subjects using different methodologies.

Sid's Bookshelf: Elevate Your Personal and Business Potential


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