Cartels secretly manipulate markets, harming consumers, businesses, and society. By raising prices, rigging markets, and restricting competition, they lead to higher costs, lower quality, and fewer choices. In this video, María Pilar Canedo (Academic Director of the OECD-GVH Regional Centre for Competition), Marcelo Guimarães, and Beatriz Marques (Competition Experts, OECD Competition Division) explain how cartels operate – including through algorithms – and why enforcement is essential for fair markets and consumer trust. This video builds on discussions from the Competition Lab for Judges on Cartels, organised by the OECD-GVH Regional Centre for Competition in Budapest in December 2024, with financial support from the European Commission.