Which mathematical algorithm first revolutionized Amazon's product recommendation system in the late 1990s, setting the standard for modern e-commerce?

In the intersection of mathematics and retail, certain algorithms have revolutionized how stores operate and make recommendations. Behind many of today's sophisticated retail recommendation systems are complex mathematical models that analyze purchase patterns, browsing behavior, and customer preferences. These systems have transformed the shopping experience and significantly boosted sales for companies that implement them effectively.

This is a live public trivia poll on AIPolls.Net. Vote and see real-time results.

Item-Based Collaborative Filtering
Gradient Boosting Decision Trees
K-Means Clustering
Markov Chain Monte Carlo