The competitive advantage created by proprietary, longitudinal engagement data that cannot be replicated retroactively. Each engagement record adds to the dataset; each quarter of maintenance adds temporal depth. After 100 engagements across 4 quarters each, the firm possesses 400 entity-quarter observations of posture dynamics — a dataset no competitor can match without running 100 engagements themselves. The data moat makes diagnostic accuracy compound: the more engagements run, the sharper the causal model, the more precise the recommendations. The data moat is the strategic reason for rigorous engagement record documentation.