Flat additive measures erase the multilevel structure of the underlying concept.

Evidence

Since the polity measure just sums across all indicators, the multilevel structure of the democracy concept does not appear at all in the measure. Here we see another aspect of concept-measure consistency: if the concept has three levels then one should take that into account when constructing the measure. If all we had was the measure construction description—sum of five indicators—then it would be reasonable to infer that the polity concept of democracy has just two levels: the five indicators and the basic-level concept of democracy. — Gary Goertz, Social Science Concepts, 694

Categorization

• DEFINE: Clarifies concept-measure consistency as matching structural levels, not just matching content.