Though recent research indicates that the Big Five can be subsumed under a “General Factor of Personality” (GFP), considerable dissention remains about whether the GFP is a substantive trait (either a “mega”-trait or simply, positive self-evaluation), or a response artifact. To disentangle these potential explanations, we estimated GFP saturation based on scales within a single inventory (which may share response artifacts) versus between different inventories (wherein the GFP would be more substantive). Drawing on meta-analytic findings across 370 independent samples of 155,781 individuals, GFP saturation was reduced substantially when based on between inventory data (26%) compared to within inventory data (50%). These results indicate that the GFP functions as a response artifact that may be reduced by administering scales from different inventories. However, some GFP variance also appears to represent stable tendencies that span across inventories. Overall, the GFP appears to be partly a stable, self-evaluative trait and partly a set of response tendencies specific to a particular personality inventory. We discuss the implications of these results for academic and applied personality measurement.