Following the publication of the CMA housebuilding report, letters were sent out to various companies in the industry. The letters likely address concerns raised in the report, such as potential anti-competitive practices or market distortions. This action indicates that the CMA is actively monitoring the industry and may take further steps, such as investigations or enforcement actions, if necessary. The affected industry includes housebuilding companies, while other companies in related sectors may also take note of the CMA's actions to ensure compliance with competition law.