Appraisal confusion - opinion of market rent

[Caitlin Worrell]

Can someone help me understand how appraisers generate the values during the appraisal process? I am reading our appraisal report and trying to make sense of it.

We own a duplex and occupy one of the units. Back in November we had an appraisal as part of an attempted refinance. We estimated that the value of our unit (2 beds/2 baths) is about $2,200, and the opinion of market rent was $1,995. The second unit (2 bed/1 bath) is currently rented at $1,600 a month, but on the appraisal report, the opinion of market rent was $1,500. The appraiser was aware that the unit was rented at that price.

I can understand that the figure would be different for the unit that isn’t actively rented, but I don’t understand how the opinion of market rent would be less than actual rent. Any ideas??