In terms of affiliated churches

• Global Membership: The Reformed tradition, broadly defined to include Presbyterian, Congregationalist, and United churches, accounts for an estimated 85 to 100 million members worldwide, or approximately 0.9% to 1% of the global population.
• Protestant Landscape: Within Protestantism, the Reformed family is one of the larger denominations. However, in the U.S., only about 31-32% of Protestant pastors identify their church as "Calvinist or Reformed", a figure that has remained stable for a decade.
• Challenges in Counting: The actual percentage is hard to pin down because:
• Many churches, especially non-denominational ones or certain Baptist groups, may affirm some Calvinist doctrines (like the "five points") without formally identifying as "Reformed".
• Many united churches have merged Reformed traditions with other Protestant branches. 

In terms of influence on the history of school of theology

• Foundational Role: Key figures like John Calvin founded institutions, such as the Academy in Geneva, that became models for later universities (like Oxford, Cambridge, and Heidelberg) and focused on rigorous, biblically-grounded systematic theology and the training of a highly educated clergy.
• Emphasis on Education: The Reformed tradition emphasized universal education so that all believers could read and interpret the Scriptures for themselves (the "priesthood of all believers" doctrine), which spurred the development of public schooling, the printing industry, and extensive libraries.
• Curriculum Development: The structure and focus of the seminary curriculum, including the intensive study of biblical languages (Latin, Greek, and Hebrew) and systematic theology, were heavily shaped by the educational reforms initiated by the Reformers.