According to Fannie Mae (FNMA) which can be found at Internet site: (www.efanniemae.com(, the following applies to appraisers. "It is expected that the appraiser will utilize generally accepted appraisal standards and the appraisal report forms which require the appraiser to research, analyze, and report on the factors in the neighborhood that may affect the market value or marketability of the properties in the market area."
FNMA goes on to state that the appraiser is ultimately responsible for leveraging industry tools and data to monitor the market conditions to ensure that the appraisal reflects an accurate indication of value. FNMA provides several possible sources for information to aid in the process to address market values and/or supply and demand. These data sources include OFHEO (Office of Federal Housing Oversight) index (www.OFHEO.gov), NAR (National Association of Realtors) (www.realtor.org) statistics on changes in median prices and S&P/Case Shiller Index (www2.standardandpoors.com). There are others available, but perhaps not on a national basis. It is the appraiser's responsibility to utilize those data sources that are deemed to be appropriate and to utilize the information to develop an informed value conclusion. The value conclusion would need to consider the current market and the potential of an over supply of dwellings being available and the possibility of value decreases.