I've actually quizzed TCAD appraisers and outside appraisers who argue on behalf of commercial clients to TCAD on this and there's a general skepticism outside of TCAD's office on any consistent methodology produced by a mass appraisal.  
 
	If you follow values, you might expect to see (based on MSA appraisal data) 5% or so annual unimproved value increases in the years 2014-2019 (I usually cite those because they were the most recent before the pandemic disrupted the market) and declining improvement values to reflect age related depreciation* (you wouldn't expect to see that on every property, but that would represent the mean outcome). 
 
	Anyway, that's not what you'll see--land values jump around, sometimes they adjust downward, then increase the improvements value, sometimes both go up, sometimes both go down (a lot of that in the last year).  
 
	You are correct, however, in that scarcity of comparable sales leads to a lot of distorted "market" valuations.  
 
	 
 
	*somewhat in defense of this, improvement value doesn't linearly do anything--it might depreciate based on age, or increase based on replacement cost factors.