Which mathematical concept was instrumental in the development of Amazon's product recommendation system that reportedly drives 35% of their total sales?

Modern retail success depends heavily on mathematical models and algorithms. From inventory optimization to customer behavior prediction, mathematics drives retail decisions worth billions of dollars annually. This trivia question explores how a specific mathematical concept revolutionized retail product development and customer engagement strategies, separating the casual retail observers from those who understand the analytical foundations of today's shopping experiences.

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Collaborative filtering using matrix factorization
Bayesian probability networks
Monte Carlo tree search algorithms
Markov decision processes