The 25 countries that showed the largest improvement in their Total CCE Index score between 2021 and 2025, accompanying the publication "The Circular Carbon Economy Index 2025: Results." The dataset includes each country's income group, region, and the breakdown of improvement across the CCE Performance and CCE Enablers sub-indices, along with detailed changes in key sub-dimensions: Energy efficiency, Fuel switching, Clean energy, Electrification, Natural sinks, and Material efficiency and waste management. This dataset highlights which countries have made the most progress on the road to net-zero over the past five years.