A residential site adjoins a rendering plant. How should the effect be measured?
Correct Answer
B) By comparing sales similarly affected nearby
Why this is correct: The impact of an external nuisance (external obsolescence) is best measured by analyzing market data—specifically, by comparing sales of properties similarly affected by the nuisance to sales of otherwise similar properties that are not affected. Why the other choices are wrong: Deducting the plant's costs is irrelevant. Using a fixed percentage is arbitrary and not market-derived. External factors must be considered in market value appraisals. Exam tip: Measure external obsolescence with paired sales or comparison to unaffected properties.
Why This Is the Correct Answer
Option B is correct because comparing sales similarly affected with otherwise comparable unaffected sales extracts the market's own measure of the penalty. That paired analysis reflects how buyers actually price the odor, traffic, and stigma rather than how the appraiser imagines they would. The technique also captures the way the effect fades with distance, since sales at varying proximity reveal a gradient. Where rental data is available, capitalizing the rent differential provides a useful cross-check on the paired sales conclusion.
Why the Other Options Are Wrong
Option A: By deducting the plant's own operating costs
The plant's operating costs are its owner's business expense and have no relationship to what the adjoining residential property is worth. A facility could be cheap or expensive to run while producing exactly the same odor and traffic. The measure of external obsolescence is the reaction of buyers of the subject, not the finances of the offending use.
Option C: By assuming a fixed twenty percent reduction
A fixed twenty percent reduction is an unsupported rule of thumb that would apply the same penalty to a house across the street from the plant and one half a mile downwind. External obsolescence varies with distance, wind, visibility, and market tolerance, so a single figure cannot be right in more than one situation. Adjustments must be extracted from market evidence, and an arbitrary percentage invites a credibility challenge.
Option D: By ignoring it, as external factors are excluded
External influences are squarely within the appraisal, not excluded from it; external obsolescence is one of the three forms of depreciation precisely because forces outside the boundaries affect value. Ignoring an adjacent nuisance would overstate value and produce a misleading report. The influence is also usually the single most important value factor in a fact pattern like this one.
Let the neighbors price the smell
You cannot move the plant and you cannot guess the discount. Find buyers who already paid to live next to it and read the number off their transactions.
How to use: Whenever a stem introduces an off-site nuisance and asks how to measure the effect, choose the market-comparison answer. Reject fixed percentages, the offending party's finances, and any suggestion to ignore it.
Exam Tip
Check where your comparables came from. Sales inside the affected area already reflect the influence, so adjusting them again would double-count the penalty.
Common Mistakes to Avoid
- -Using a rule-of-thumb percentage for an external influence
- -Double-adjusting comparables that are themselves within the affected area
- -Treating an incurable external influence as curable physical deterioration
- -Failing to allocate external obsolescence between land and improvements in the cost approach
Concept Deep Dive
Analysis
This tests the measurement of external obsolescence, the loss in value caused by influences outside the property boundaries. A rendering plant produces odor, truck traffic, and stigma, none of which the owner can cure, so the loss is incurable and must be measured rather than remedied. The reliable technique is paired data analysis: find sales of properties subject to the same influence and compare them with otherwise similar sales outside the affected area, letting the price difference reveal what buyers actually deduct. A second approach capitalizes the rent loss attributable to the influence where rental data exists, converting a recurring income penalty into a value figure. Both are market-derived, which is the point, because external obsolescence varies enormously with distance, prevailing wind direction, visibility, and how long the nuisance has operated. Note also that the effect falls on both land and improvements, so an appraiser using the cost approach must allocate it appropriately.
Background Knowledge
You need to know that external obsolescence arises outside the property lines, is generally incurable, and is measured by paired sales analysis or by capitalizing the attributable rent loss. You should also understand that the effect typically diminishes with distance, that it burdens both land and improvements so allocation matters in the cost approach, and that comparables drawn from within the affected area may already reflect the influence.
Real-World Application
Valuing a house three lots from a rendering plant, you assemble sales within the odor zone and matched sales in the same subdivision beyond it. The pairs indicate roughly an eleven percent discount that narrows with distance, so you support the adjustment with those pairs and describe the gradient in the report.
More Land/Site Questions
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Why can the same physical parcel carry different values in two assignments?
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