The International Country Risk Guide (ICRG) Institutional Index is a measure of the strength and effectiveness of a country's political institutions. The data is proprietary and is available for purchase from the PRS Group, the organization that produces the ICRG. You can visit their website at https://www.prsgroup.com/ and contact them to inquire about purchasing the complete ICRG dataset, including the Institutional Index.

Please note that the data is expensive and may require a subscription, so be prepared to provide information about your intended use of the data and your budget for the purchase.