Craftsman's area modification factors are percentage adjustment factors (for material, labor and equipment) by which a contractor can adjust national average costs to account for variance due to their local region. Area mod percentages are composites of many costs and will not necessarily be accurate when estimating the cost of any particular part of a building. But when used to modify costs for an entire structure, they should improve the accuracy of your estimates.
The goal of the Area mods data set is to reflect trends. In some cases, official data sources provide data with large fluctuations (i.e. unrealistic and impractical for direct use in the area modification calculations). In those cases, we incorporate a smoothing/trending methodology.