Portland Area Real Estate Appraisal Discussion

Appraisers and real estate agents often ask what adjustments I use and/or how I support my adjustments.  The answer is that most properties require a different adjustment that is specific to its market (e.g. size, location, condition, etc.) and there are many different ways to support any individual adjustment.  No one method for supporting adjustments is perfect.  Appraisers should select the method or methods that will produce credible results for the given assignment and available data. 

I recently appraised a roughly 1,200 square foot 1970s ranch home on a city-sized lot in a Portland suburb wherein the quantity and quality of the available data was particularly good.  For this reason, I was able to have a little fun and support my appraisal adjustments for this one assignment in many different ways.  Here are the multiple approaches and real data for supporting my Gross Living Area (GLA) adjustment.  (Information that may identify the subject or comparable sales have been redacted for confidentiality.)

  1. Paired Sales – Paired sales are a cornerstone of textbook appraisals, but textbook cases of paired sales rarely occur in practice. In a common textbook scenario, paired sales are two sales that are the same in every way except the one factor for which the appraiser is trying to estimate an adjustment. For this reason, it is easy for appraisers to forget that a paired sale can have other differences (although it is important that the differences are minimal and that adjustments for the differences can be supported). In this assignment, my grid included four sales that had very little difference from one another except for GLA. After adjusting for a couple of minor factors, the paired sales all suggested an adjustment of $51 and $60 per square foot for GLA.
  2. Simple Linear Regression – I’ve blogged in the past about supporting adjustments, particularly GLA, using simple linear regression. Linear regression is basically analyzing trends in data. (Here is a link to the most-recent post and to a video on how I use this tool.) For this assignment, simple linear regression suggests $53 per square foot when comparing sales price to GLA. Significant variation exists among the data of this sample, but the datum points are spread evenly along the entire regression line suggesting that the indicator is not being skewed by a small subset of outliers. It is okay if the properties in the sample have differences, however it is important to make sure to filter out differences that would skew toward one end of the range or the other. For example, if a larger site size also tends to include a larger home, then it would be important to make sure that the homes in the sample all have similar site sizes or the adjustment could be falsely overstated. Also, it is helpful to the outcome of the regression analysis that the subject property is in similar condition to the majority of the sales in the sample. The following chart shows the linear regression outcome in this appraisal.

    Simple Linear Regression Support Adjustment 

  3. Grouped Data Analysis – This method is closely related to simple linear regression and is essentially many paired sales representing a fast way to estimate an adjustment simply by sorting comparable sales. This can be done using quick searches on the local multiple listing service or using data exported to a spreadsheet. But remember that the same factors that can skew linear regression will also skew grouped data analysis. For best results, it is important to sort out all of the features that might distort the results without sorting to the point where the sample sizes are small and wildly varied. For this assignment, I filtered out all ranch sales in the past two years with a lot size of 7,000 to 9,999 square feet, that feature two baths and three bedrooms, and that were built within ten years of the subject. Sales of homes meeting these criteria between 1,000 and 1,199 square feet have an average of 1,128 square feet and an average sale price of $212,637. Sales of homes meeting these criteria between 1,200 square feet and 1,299 square feet have an average of 1,253 square feet and an average sale price of $220,055. The difference between the average of these two sets is $7,418 and 125 square feet or $59 per square foot. The median could also be compared as well to provide another indicator that is less likely to be skewed by outliers.
  4. Depreciated Cost – The cost approach value in this assignment is consistent with values suggested by recent comparable sales. This suggests that the cost approach is likely valid and could be used as a way to test reasonableness or support adjustments. The subject’s original cost is estimated at $108 per square foot and the depreciated cost is estimated at $81 per square foot. A simple depreciated cost adjustment might not be a good adjustment to apply to comparable sales. This is because the depreciated cost is a straight-line measure from zero square feet all the way to the total area including the kitchen, bath, mechanical, and everything else in the house. For this adjustment, we are just looking for the value difference from a similar-sized comparable to the subject. To obtain this adjustment using the cost approach, I ran a cost estimate for the smallest comparable sale and another cost estimate for the largest comparable sale with no physical changes for anything other than living area (e.g. room count, garage, quality, and all other factors kept equal). The original cost difference between the low and the high came out to $79.53 per square foot. If this number is depreciated based on the cost approach in the appraisal, a reasonable adjustment of $60 per square foot of GLA is estimated.
  5. Income Approach – The income approach was not performed for this appraisal assignment, but if it had been, the income approach could have been used to support another indicator for the GLA adjustment. One way the income approach could be used to support a GLA adjustment is by taking the estimated loss or gain in rent from an additional square foot of living area (can be estimated using any of the above approaches except for cost) and apply a Gross Rent Multiplier (GRM). Critical to this approach is that the multiplier and rent estimates are market derived and that rent might be a consideration for the typical buyer.
  6. Sensitivity Analysis – This method is closely related to paired sales and I think it works best for secondary or tertiary support for an adjustment or helping to reconcile what adjustment is most effective. However, this method is not very useful if adjustments for other comparable sale differences are not accurate. Once all of the comparable sales have been placed side-by-side in a comparison grid and adjusted for all other factors using market derived adjustments, the appraiser can test different GLA adjustments to see what adjustment produces the tightest range of adjusted value indicators. If the appraiser is unsure by simply looking at the data, the Coefficient of Variation (CV) can be applied to each set of adjusted indicators to mathematically test what adjustment is producing the tightest range. The lower the CV, the better the adjustment is working within this sample of sales. Here is a link to a free CV calculator. Just enter your adjusted indicators separated by commas and press calculate. Then test another adjustment and repeat with the calculator. An appraiser could also set up a formula using the Worksheet function in a la mode Total to instantly provide the Coefficient of Variation. For this appraisal, sensitivity analysis helped me reconcile that the simple linear regression adjustment is most well-supported adjustment because it has the lowest CV as seen in the following table.

Paired Sales

Simple Linear Regression

Grouped Data

Depreciated Cost

Indicated GLA Adjustment

$51 or $60





0.00648 or 0.0082





None of the above methods for supporting an adjustment are without limitations and there are many more ways an appraiser could support an adjustment.  Although this is an example where data sets are particularly plentiful, the example shows that information does exist outside of textbooks for supporting adjustments; and when multiple approaches are combined and reconciled, a strong case for the appraiser’s conclusion can be made.  An appraiser won’t always need to go this far to support one adjustment, but if that one adjustment is crucial to the outcome of the appraisal or the appraiser believes they will be challenged on this adjustment, then the appraiser should expand and explore multiple methods for support.

Did I leave anything out or do you want to join in the conversation?  Let me know in the comments below.

If you find this information interesting or useful, please subscribe to this blog and like A Quality Appraisal, LLC on Facebook.  Also, please support us by making Portland real estate appraisal related comments on our blogs and YouTube videos.  If you need Portland, Oregon area residential real estate appraisal services for any reason, please request appraisal fee quote or book us to speak at your next event.  We will do everything possible to assist you.

Thanks for reading,

Gary F. Kristensen, SRA, IFA, AGA

Appraisers in Portland, Oregon and everywhere else are talking about supporting adjustments, due mostly to fears of Fannie Mae’s new Collateral Underwriter (CU).  Supporting adjustments can be an important part of producing a credible opinion of value and I often blog about adjustments.  However, when reviewing the reports of other appraisers, I frequently have very different opinions on the adjustments applied, but then just as often, the other appraiser comes very close to the same value conclusion that I would reach.  So how is that possible?  The key lies in understanding qualitative and quantitative analysis.

Appraisers often use both qualitative and quantitative analysis when making comparisons.  Qualitative analysis means that the appraiser is recognizing distinctions and ranking the comparable sales in terms of superior, inferior, or similar, rather than actually trying to measure the difference or apply adjustments.  Quantitative analysis means that the appraiser is making a “quantity” of dollar or percentage adjustment to comparable sale prices (for recognizable differences) to arrive at an indication of value for the subject property.

Qualitative Analysis

Qualitative analysis simulates the thought process of a typical buyer who is simply trying to find the most home for the least amount of money.  Qualitative analysis is also a quick way for real estate professionals to arrive at a value conclusion when there are plenty of comparable sales, and it can additionally be an accurate way to check the reasonableness of the results in a quantitative appraisal.  Some appraisers will make an adjustment grid for qualitative analysis that looks like any other adjustment grid, but instead of making dollar adjustments, the appraiser will just place plus and minus symbols (most common in commercial appraisal).  Some appraisers might use multiple minus or multiple plus symbols when a factor is much superior or much inferior to the subject.  Sometimes a qualitative analysis might just be an ordering or ranking of the comparable sales by price to see where the subject’s value would most likely fall as in the following example.

In the above qualitative example, comparable sales are ranked from lowest to highest sale price.  It is easy to see that the subject is nearly as large as Comparable 3, is the same age, has almost the same size lot, and has the same garage count.  Based on a qualitative analysis of the above sales, the appraiser should reconcile a value that is close to Comparable 3 and significantly more than Comparable 1 and 2.  Anything more than the sale price of Comparable 3 ($325,000) would not be reasonable given only the above information.

Quantitative Analysis

Quantitative analysis is a required process in most appraisals for residential lending where federally backed loans are obtained.  The strength of quantitative analysis is that it can be more precise and, when performed correctly, provides the appraiser with a tighter and more accurate range of value indicators.  One problem with quantitative analysis is that it can be very difficult for appraisers to support some adjustments, and if those adjustments are incorrect, may lead the appraiser to the wrong conclusion or a point of contention that could damage the credibility of the entire appraisal.  However, the following examples show that, if the appraiser is paying attention to the qualitative ranking of the comparable sales and is reconciling thoughtfully (rather than with an average), the value conclusion could be credible, even if the adjustments are not.

In the above example, the important factors are quantitatively accounted for using dollar adjustments.  Comparable 1 and Comparable 2 have not been adjusted for age because the agents explained that these two properties were particularly well cared for, lightly lived in, and freshly painted.  Site size is not adjusted because the small differences are not estimated to be noticeable by the buyers in this market.  The garage and GLA are accounted for and the tight range of adjusted indicators from $319,000 to $322,100 suggests that the estimated adjustments are reasonable.  Consequently, it should be easy for the appraiser to reconcile within this range.

The next table shows the same comparable sales with very different adjustments applied by the appraiser.

In this example, a different appraiser has adjusted half as much per square foot of living area, half as much for the garage, and has estimated that the older properties require an age or condition adjustment.  These are all reasonable conclusions in the lack of other evidence supporting the adjustments.  Here, two of the comparable sales, including the strongest, have adjusted value indicators that are within the range of the data in the prior sample.  It is easy to see that even with dramatically different adjustments, the appraiser will likely still reconcile the same value conclusion for the subject with most weight to the strongest of the indicators (Comparable 3). 

The above two examples show:

  1. Appraisers might have dramatically different opinions of adjustments and might still come to the same value conclusion because they have thoughtfully employed both qualitative and quantitative analysis in the appraisal process.

  2. Qualitative analysis can be a quick way to come to a value conclusion and a handy way to test the reasonableness of appraisal conclusions. 

Did I leave anything out or do you want to join in the conversation?

Let me know in the comments below.

If you find this information interesting or useful, please subscribe to this blog and like A Quality Appraisal, LLC on Facebook.  Also, please support us by making Portland real estate appraisal related comments on our blogs and YouTube videos.  If you need Portland, Oregon area residential real estate appraisal services for any reason, please request appraisal fee quote or book us to speak at your next event. We will do everything possible to assist you.

Thanks for reading,

Gary F. Kristensen

February 25th, 2015 10:19 AM

Recently, I performed an appraisal on a very unique property that sold in 2006 after a normal time on the market.  Other than maintenance, the subject did not change noticeably in nine years.  This is an upper end property near Portland, Oregon; an area where such home prices have not recovered as much as lower priced and median priced properties have since the mortgage meltdown.  Consequently, the S&P/Case-Shiller Portland Home Price Index would not be a good way to ballpark the current value or the market appreciation adjustments for this subject, because the index is derived from properties at all price levels and locations across Portland.

The Case-Shiller Portland Index was 181.02 in August of 2006 and the most recent Index (November 2014) is 170.44.  Case-Shiller suggests a price decline of roughly six percent, or that the subject’s current value should be $740,000 rounded.  However, this information can confuse an appraiser, given that all of the adjusted comparable sales are pointing closer to a value of $650,000.  Based on this, some appraisers or real estate agents might think that the prior sale is not relevant at all.  The problem is not with the prior sale being relevant, but that the published market data are not relevant to this property.

The Case-Shiller Index and other published market data, like multiple listing market reports, are great for looking at the overall market, but they do not apply to most individual properties as an adjustment.  Conversely, if the appraiser performs a search of only comparable sales that are similar to the subject over the past nine years, and plots them on an Excel scatter chart with a polynomial trend line, it is easy to see that the prior sale is relevant and consistent with the adjusted comparable sales.

The Nine-Year Trend chart (above) shows that a value for the subject close to $650,000 is reasonable, and that a value at $740,000 (as suggested by the Portland Case-Shiller Index) would not be reasonable.  A value of $740,000 would be above the sales price of anything similar that has sold in the past two years.  The Nine-Year Trend chart shows that when the subject last sold, it was at the upper end of the market for similar properties, but it was not at the top of the market (nor above the market) because there were many properties that sold for more.  The Nine-Year Trend chart, in addition to an appraiser’s comparable sales analysis, shows that this subject’s prior sale is relevant after many more years than the three years that appraisers are required to analyze a prior sale.

Did I leave anything out or do you want to join in the conversation?  Let me know in the comments below.

If you find this information interesting or useful, please subscribe to this blog and like A Quality Appraisal, LLC on Facebook.  Also, please support us by making Portland real estate appraisal related comments on our blogs and YouTube videos.  If you need Portland, Oregon area residential real estate appraisal services for any reason, please request appraisal fee quote or book us to speak at your next event.  We will do everything possible to assist you.

Thanks for reading,

Gary F. Kristensen


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