Index methodology transparency: require published methods, stakeholder consultation, periodic review and advance notice of changes. Regulation 19 mandates that the Index Provider document and publicly publish the methodology for Index calculation and maintenance to permit assessment of representativeness and appropriateness. The methodology must include timeframes for changes to Index constituents allowing sufficient implementation time. The Index Provider shall seek market feedback for significant changes, periodically review methodology to ensure adherence to objectives, consult stakeholders including market participants and subscribers before implementing changes, and provide advance notice of proposed methodological changes.