A pool costs $70,000 to install but adds $25,000 to a home's sale price. What does the principle of contribution say its value is?
Correct Answer
D) $25,000, what it adds to the whole
Why this is correct: The principle of contribution states a component's value is measured by its net contribution to the total property value, not its cost. Here, the pool adds $25,000 to sale price, so its contributory value is $25,000. Why the other choices are wrong: "$70,000, its documented cost" is incorrect; cost does not equal value. "$47,500, a compromise figure" is wrong; contribution is not an average. "Nothing, since it failed to return cost" is false; it added value, just less than its cost. Exam tip: Contribution = value added. Cost is irrelevant to the buyer.
Why This Is the Correct Answer
Option D is correct because the principle of contribution defines the component's value as what it adds to the whole, which the stem states is $25,000. The measurement is complete once the market's response is known; no reconciliation with cost is required or permitted. The remaining $45,000 is simply money the owner spent that the market will not return, which is a real economic outcome rather than a computational problem. Reporting $25,000 is both the correct application of the principle and the figure a buyer's behavior actually supports.
Why the Other Options Are Wrong
Option A: $70,000, its documented cost
Cost measures what was spent to create the improvement, and value measures what the market will pay for it, and the two coincide only under specific conditions. Treating documented cost as value would overstate this property by $45,000 and would embed the owner's spending decision into a market value opinion. Cost data are still useful, but as an input to be tested against market reaction, never as a substitute for it.
Option B: $47,500, a compromise figure
Averaging cost and contribution produces a number with no economic meaning, since nothing in the market supports a figure halfway between what one owner spent and what buyers pay. Appraisal conclusions are derived from evidence, not from splitting the difference between competing figures. The compromise instinct is exactly what the principle of contribution is meant to discipline.
Option C: Nothing, since it failed to return cost
The improvement did add value, just less than it cost, so concluding zero contribution ignores the $25,000 the market demonstrably pays. Zero contribution would be correct only if paired sales showed buyers indifferent to the feature, and a negative contribution is possible when a feature actively deters buyers. Failing to recover cost and contributing nothing are two different findings, and the stem states which one occurred.
The Whole Answers the Question
To value a part, ask the whole. Take the property with the pool and the same property without it, and the difference between the two is the pool's value. The invoice never enters the conversation, because the buyer did not pay the invoice; the buyer paid the price.
How to use: Whenever a stem supplies both a cost figure and a market response figure, the market figure is the answer and the cost figure is the distractor. Watch for a third choice that averages the two, which is always wrong. Then check whether the question wants the contribution itself or the shortfall, which is the functional obsolescence.
Exam Tip
Read carefully whether the question asks for contributory value or for the amount of obsolescence; in this fact pattern those are $25,000 and $45,000, and both numbers will appear among the choices in related items.
Common Mistakes to Avoid
- -Adding the full cost of a recent improvement to the value conclusion
- -Averaging cost and market contribution to reach a compromise figure
- -Assuming an improvement that fails to return its cost contributes nothing at all
Concept Deep Dive
Analysis
This question tests the principle of contribution in its cleanest form. Contribution holds that the value of any component of a property is measured by how much it adds to the value of the whole, or alternatively by how much its absence would subtract, and not by what it cost to create. The gap between the $70,000 spent and the $25,000 added is not an error; it is the ordinary result when an owner installs an improvement the market does not fully reward, and the $45,000 difference is a form of functional obsolescence arising from over-improvement. Cost and value coincide only when an improvement is at or near the property's highest and best use, is new, and suits typical buyer preferences in that market. Appraisers meet this constantly with pools, elaborate landscaping, high-end kitchen remodels, and outbuildings, where personal preference drives spending well past what a buyer pool will pay. The correct measurement always comes from market evidence, typically paired sales, rather than from invoices.
Background Knowledge
You need to know the principle of contribution and its relationship to the principles of substitution, balance, and increasing and decreasing returns, and to recognize that a shortfall between cost and contribution is functional obsolescence from over-improvement. You should also know that contributory value is measured from market evidence such as paired sales, and that cost figures enter the analysis only when supported by market reaction.
Real-World Application
A homeowner who spent $70,000 on a pool asks why the appraisal did not reflect it. The appraiser shows six paired sales in the subdivision indicating pools contribute roughly $22,000 to $28,000, explains that contributory value is measured by buyer behavior, and identifies the difference as an over-improvement for that price range.
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