Both Stewart Butterfield and Joel Greenblatt built their fortunes by turning ideas into highly influential businesses, but their paths could hardly be more different. Butterfield is a Canadian technology entrepreneur best known for Flickr and Slack, while Greenblatt is an American investment manager whose reputation rests on Gotham Capital, value investing and the “Magic Formula.” Their careers span technology, finance, education and philanthropy, with both becoming self-made figures whose influence extends well beyond their original ventures.
Stewart Butterfield and Joel Greenblatt Quick Bio
| Category | Stewart Butterfield | Joel Greenblatt |
|---|---|---|
| Full Name | Daniel Stewart Butterfield | Joel Michael Greenblatt |
| Date of Birth | March 21, 1973 | December 13, 1957 |
| Age | 53 years (September 2026) | 68 years (September 2026) |
| Net Worth | About $1.5–$1.6 billion, estimated; Forbes lists him among its 2026 billionaires. | About $1 billion, estimated; there is no authoritative current Forbes personal figure, so estimates vary. |
| Birthplace | Lund, British Columbia, Canada | Great Neck, New York, USA |
| Nationality | Canadian | American |
| Profession | Entrepreneur, technology executive, designer, investor and philanthropist | Investor, hedge-fund manager, author, educator and philanthropist |
| Best Known For | Co-founding Flickr and Slack | Founding Gotham Capital and developing the Magic Formula investing approach |
| Major Company | Slack Technologies / Flickr | Gotham Capital / Gotham Asset Management |
| Career Field | Technology, software, internet and digital communications | Finance, investment management and value investing |
| Early Entrepreneurial Venture | Ludicorp, founded in 2002 | Gotham Capital, founded in 1985 |
| Flickr Connection | Co-founded Flickr, which grew out of Ludicorp’s Game Neverending project | No direct connection |
| Slack Connection | Co-founder and former CEO of Slack | No direct connection |
| Major Acquisition | Salesforce acquired Slack for approximately $27.7 billion in 2021 | Gotham Capital evolved into Gotham Asset Management |
| Investment Style | Technology entrepreneurship and startup investing | Value investing and special situations |
| Signature Idea | Building communication and social platforms around internet communities | “Magic Formula” investing — combining business quality and attractive valuation |
| Education | University of Victoria — B.A.; Clare College, Cambridge — M.Phil. in Philosophy | University of Pennsylvania, Wharton — B.S., 1979, summa cum laude; M.B.A., 1980 |
| Additional Education | Self-taught programming from childhood | Studied at Stanford Law School for about one year before leaving for finance |
| Academic Career | Primarily technology and entrepreneurship rather than university teaching | Taught Value and Special Situation Investing at Columbia Business School for more than two decades |
| Major Books | No major investment-book career | You Can Be a Stock Market Genius, The Little Book That Beats the Market, The Little Book That Still Beats the Market, The Big Secret for the Small Investor, Common Sense |
| Investment Track Record | Fortune primarily created through technology-company equity | Gotham Capital achieved an exceptional historical record; sources report roughly 50% annualized gross returns from 1985–1994 and about 34.4% net over that period. |
| Current Professional Role | Entrepreneur, investor and board/philanthropic participant | Managing Principal and Co-Chief Investment Officer of Gotham Asset Management |
| Company Today | Associated with technology, investment and philanthropic activities following Slack | Gotham Asset Management continues to manage value-oriented investment strategies |
| Parents | David and Norma Butterfield | Allan and Mickey Greenblatt |
| Siblings | Family details are less extensively documented publicly | Richard Greenblatt and Sharon Curhan are publicly associated with his family |
| Marital Status | Separated/divorcing from Jennifer Rubio in 2026 after six years of marriage; they remain co-parents. | Married to Julie Greenblatt |
| Former Spouse | Caterina Fake, Flickr co-founder; married 2001–2007 | — |
| Children | Three: Sonnet from his first marriage and Oliver and Francesca with Jennifer Rubio. | Five children are publicly associated with his family |
| Family Life | Known for maintaining a high-profile family and philanthropic life with Jennifer Rubio; now co-parenting after their separation | Keeps much of his family life private while remaining active in education and philanthropy |
| Height | Around 5 ft 10 in–6 ft (178–183 cm), estimated/reported | Around 5 ft 4 in (165 cm), commonly reported but not officially verified |
| Weight | Around 165–175 lb (75–79 kg), estimated | Around 132 lb (60 kg), commonly reported estimate |
| Hair Color | Brown/dark brown, later gray | Gray/white |
| Eye Color | Blue/gray, commonly reported | Brown/dark brown, commonly reported |
| Hobbies & Interests | Technology, programming, photography, design, architecture, art, gardening and music | Investing, reading, teaching, education, philanthropy and family |
| Public social-media presence exists, but personal-account verification should be checked before treating an account as official | No clearly verified official personal Instagram account identified | |
| Major Philanthropy | Rubio Butterfield Foundation; major cultural and educational giving, including a $23M+ Met internship pledge | Education, Success Academy, University of Pennsylvania and other educational/medical initiatives |
| Education Connection | University of Victoria and Cambridge | Wharton School and Columbia Business School |
| Teaching | Not principally known as an academic teacher | Longtime Columbia Business School adjunct professor |
| Entrepreneurial Reputation | Serial technology entrepreneur who helped shape modern online communication | Legendary value investor and investment educator |
| Major Achievement | Helped create Flickr and Slack, two influential internet platforms | Built Gotham Capital and popularized systematic value investing through the Magic Formula |
| Business Philosophy | Build useful products, understand users and create enduring technology businesses | Buy quality businesses at attractive prices and remain patient |
| Public Reputation | Innovative, design-oriented Silicon Valley entrepreneur | Disciplined, analytical value investor and teacher |
| Legacy | Flickr and Slack helped reshape online photography and workplace communication | Helped make sophisticated value-investing concepts accessible to ordinary investors |
| Current Age Difference | — | 15 years older than Butterfield |
| Wealth Difference | Considerably wealthier by current public estimates | Wealthy, but current personal net worth is less reliably documented |
| Overall Field | Technology & Entrepreneurship | Finance & Investment |
| Most Recognized Name | Slack | Magic Formula Investing |
| Career Type | Founder → technology executive → investor/philanthropist | Investor → author → professor → philanthropist |
| Overall Influence | Technology, workplace software, photography and internet culture | Value investing, financial education and philanthropy |
Stewart Butterfield and Joel Greenblatt Images
