MPAC has approximately 1500 employees, but this includes management, admin, and technology. This leaves well below 1500 actual assessors to value over 5 million properties. It is perhaps not surprising that data errors arise.
But the process the assessors use, especially for industrial type properties, is complicated, and it can be very difficult to find the errors. Every building, every change in height, age or construction, has dozens of separate data points in the assessor's records. I helped in the initial launch of MPAC's Automated Cost System ("ACS") - and I excel in finding how it has been misapplied.