1.5.4.3. Expense Analysis. In developing the estimate of net operating income that will be capitalized to develop an opinion of the market value of the subject property, the appraiser must collect market data to support the estimated vacancy and credit loss, as well as operating expenses and any set asides for reserves for replacement. If available, the operating history of the subject property provides an important basis for these estimates, but data collected from other similar competitive buildings in the market area is also important to provide market support for these determinations.