Founders of the meal delivery service Blue Apron, health insurance startup Oscar, and content delivery network CloudFlare all pursued business degrees at Harvard Business School. Altogether, 23 of the Boston Ivy’s MBA students have founded a private company valued at $1 billion or more, according to research from enterprise software company Sage.

With 19 unicorn founders, the Stanford Graduate School of Business comes in second, followed by UPenn’s The Wharton School, with nine.

It’s important to note, however, that for undergrads, Harvard and Stanford swap places: Stanford’s undergraduate program has produced 51 founders of billion-dollar startups, followed by Harvard with 37.

Below are the top business schools, ranked by how many of their students and alumni went on to found billion-dollar companies.

Note: Founders are classified based on their highest level of education. (For instance, if they received a Master’s degree at Harvard University and a PhD at Stanford Business School, they would be placed in the latter category.) The list also includes founders who didn’t graduate. For more information, see a breakdown of the research here.

• Harvard Business School: 23
• Stanford Graduate School of Business: 19
• University of Pennsylvania, Wharton: 9
• INSEAD: 5
• WHU – Otto Beisheim School of Management: 5
• University of Southern California: Marshall: 4
• University of California at Berkeley: Haas: 3
• Columbia Business School: 3
• HEC Paris: 3
• Indian Institute of Management: Calcutta: 3
• UCLA Anderson School of Management: 2
• Brigham Young University: Marriott: 2
• George Washington University: 2
• London Business School: 2
• Northwestern University: Kellogg: 2
• University of Illinois at Urbana-Champaign – College of Business: 2