All adjustments are imprecise. That becomes evident when you develop your adjustments 2 or 3 different ways. If readers or courts misconstrue a number in your report for a level of precision that doesn't exist, then all your adjustments and your final OMV are also open to that same criticism. The point of making adjustments is to build a credible valuation model, and that often doesn’t require precision.
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This is from The Appraisal of Real Estate 14th Edition:
Qualitative Analysis-Relative Comparison Analysis
Reliable results can usually be obtained by bracketing the subject between comparable properties that are superior and inferior to it. If the comparable properties are either all superior or all inferior, however, only an upper or lower limit of values is set and no range (or bracket) of possible values for the subject can be defined. For example, if all the comparable properties are inferior in terms of qualitative factors, the only conclusion the appraiser can draw is that the value of the subject property is higher than the highest value indication for the comparable properties. The appraiser must search the market diligently to obtain and analyze sufficient pertinent data to bracket the value of the subject property. If the available comparable sales do not bracket the subject's value, the appraiser should consider employing other analytical techniques to establish such a bracket. Quantitative adjustments to the comparable sales can often serve this purpose.
When it comes to using qualitative analysis for site size, it is obvious when you are bracketed. However, for market conditions, it's not possible to know if your comps bracket the subject without doing a quantitive analysis first. One of the most common things I see in appraisals is that no MC adjustment is made for sales that closed 2, 3, and 5 months ago, but that appraiser reconciles to the upper end of the range. In a market that is appreciating, the adjusted range will only represent a floor. In a market that is declining, which is possibly the OPs scenario, the adjusted range will only represent a ceiling.