Increasing safety stock to improve customer fill rate would result in a decrease in inventory turns. Inventory turns, or inventory turnover, is a metric measuring how fast the inventory is replaced over time. It is calculated as the cost of goods sold divided by the average value of inventory during the period covered1. A higher inventory turnover ratio indicates that the company sells its inventory quickly and efficiently, while a lower ratio implies that the company holds too much inventory or has difficulty selling it. Safety stock is an extra quantity of a product stored in the warehouse to prevent an out-of-stock situation. It serves as insurance against fluctuations in demand, longer lead times, and price fluctuations2. Increasing safety stock means increasing the average value of inventory, which lowers the inventory turnover ratio. This also increases the inventory carrying costs, such as storage, insurance, taxes, and obsolescence. Therefore, there is a trade-off between increasing safety stock to improve customer fill rate and decreasing inventory turns to reduce inventory costs3. Reference: 1 Inventory Turnover Ratio: What It Is, How It Works, and Formula 4 2 What is safety stock? | Definition, Importance, Formula - Zoho 5 3 CPIM Exam Reference - Association for Supply Chain Management 6

A Fourth-Party Logistics (4PL) provider assumes broader roles than a traditional third-party logistics (3PL) provider. It is not only responsible for the physical movement of goods but also for managing the supply chain as a whole, including coordination between the client and multiple logistics service providers.
"Companies that not only take on the responsibility of the physical movement of goods between a supplier and a customer but also take more of the supply chain service requirements are called a fourth-party logistics company."
- Source: CPIM SMR Study Guide - CPIM_SMR_en.pdf, Question 125