[ATTOM] Tax Assessment History Data

I am using tax assessor historical data. For some properties, the records cover consecutive years—for example, from 2003 to 2022. For other properties, there are missing years; for instance, the data may span 2003 to 2022 but exclude 2010.

What is the reason for these missing years? Does this mean the county failed to assess the property during those years? Is the default assumption that a property is assessed every year?