<p>This study investigates how firm-level strategic resources shape the predictive validity of the Net Promoter Score (NPS) in grocery retail. We propose Private Label Brand Intensity (PLBI, the share of sales from retailer-owned brands) as a loyalty amplifier that strengthens the relationship between promoter status and recommendation intentions. Using a multilevel modelling framework with customer evaluations nested within six national chains, we find that PLBI significantly amplifies the Promoter–Intention link, though with diminishing returns at very high PLBI levels, and that embedding this strategic moderator into predictive models meaningfully improves forecasting accuracy. These results advance business analytics by demonstrating that the diagnostic value of a widely used customer metric is context-dependent and systematically shaped by firm-level resource deployment. The study introduces loyalty amplifiers as a theoretical construct bridging the Resource-Based View and customer mindset metric research, and offers practical guidance for CRM system design, analytics dashboard calibration, and private label strategy in retail.</p>