Successfully transitioning to net-zero greenhouse gas (GHG) emissions requires effective mitigation policy packages, which include carbon pricing measures: a cost-effective policy instrument that not only reduces emissions but also generates revenue to support the transition. This fourth edition of Effective Carbon Rates provides an overview of the carbon pricing landscape, examining fuel excise taxes, carbon taxes, and emissions trading systems (ETSs) through 2021, with updates on developments until 2023. The policy mechanisms examined directly impact the cost of emitting GHGs, influencing shifts in production, consumption, and investment towards low- or zero-carbon options. The analysis covers 72 countries which together account for approximately 80% of global GHG emissions. The report focuses on developments in ETSs and transport fuel taxes amidst the energy crisis and provides comprehensive and comparable data on the current status of GHG emissions pricing that can assist policymakers in identifying priorities and refining carbon mitigation strategies.