IPI was introduced in 2018 to gauge inventory levels and set stock limits to help novice Amazon sellers improve their business trajectory by identifying the areas of improvement in inventory management.
According to Amazon, the Inventory Performance Index measures your inventory health and profits, it also takes into consideration how well you fix your product listing problems such as keeping popular products in stock and removing unavailable products from your listings.
https://www.sellerapp.com/blog/amazon-inventory-performance-index-ipi/
