Which retail giant first implemented the 'Collaborative Filtering Algorithm' that revolutionized product recommendations using matrix mathematics and became industry standard?

The retail industry has been transformed by mathematical modeling and data analytics. Major retailers now employ teams of mathematicians to optimize everything from inventory management to customer behavior prediction. This has created a fascinating intersection between advanced mathematics and retail innovation, with some companies investing billions in their mathematical capabilities. How well do you know the pioneers in this mathematical retail revolution?

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Amazon with its patented item-to-item collaborative filtering approach (1998)
Walmart with its customer segmentation matrix model (2001)
Target with its predictive analytics pregnancy algorithm (2002)
Netflix with its Cinematch recommendation system (2000)