The world's largest expert network - a marketplace where a single question becomes a phone call with someone who already knows the answer.
GLG's wordmark, above, designed by Michael Bierut of Pentagram. Behind the four letters sits a network of roughly one million experts and a quarter-century of turning knowledge into a callable service.
Ask a hedge fund analyst how they came to understand a niche medical-device market in three days, and there is a decent chance the answer involves GLG. Gerson Lehrman Group runs the world's largest expert network: a system for taking a client's specific question and matching it, quickly, to a person who has lived the answer. That person might be a former supply-chain executive, a practicing oncologist, a semiconductor engineer or a onetime regulator. GLG makes the introduction, arranges the call, and handles the compliance around it.
The core transaction is deceptively simple - a one-on-one consultation, usually by phone or video, between a client and a vetted expert. But GLG has wrapped that transaction in scale and process: surveys fielded across thousands of practitioners, moderated roundtables, site visits, live events, custom expert recruitment and professional-learning programs. The common thread is primary research - insight that comes directly from people, not from a report someone else already published.
The firm calls its experts Council Members and its clients members too, framing the whole thing as a marketplace for trusted human expertise. What GLG sells, in the end, is not data. It is access to the person who has the data in their head - and the confidence that comes from hearing it first-hand.
"GLG started as a publisher. Its clients didn't want the books - they wanted to talk to the authors."
GLG's clients are organizations that make high-stakes decisions on incomplete information and cannot afford to be wrong. Hedge funds and asset managers use it before taking a position. Private equity firms lean on it for diligence. Strategy and management consultancies use it to sound authoritative on markets they may have entered only weeks earlier. Corporations across life sciences, technology, industrials, energy and consumer goods use it to test messaging, size markets and pressure-check strategy. Law firms and non-profits use it too.
The problem GLG solves is time and access. The internet is full of information, but the specific, current, first-hand knowledge that moves a decision often lives in one person's experience - and that person is hard to find, harder to reach, and rarely writes it down. GLG's job is to shorten that distance: from a question to the right expert, in hours rather than weeks.
There is a second, quieter problem: doing all of this without breaking rules. Expert calls in finance and healthcare sit close to sensitive information, from material non-public data to patient confidentiality. GLG's compliance framework - expert screening, disclosure, conflict checks, monitoring - is a large part of why regulated clients keep coming back. The vetting and the guardrails, not just the roster, are the product.
One-on-one phone or video calls connecting a client to a vetted expert with first-hand knowledge of a market, company or technology.
Custom surveys fielded across the network to turn practitioner knowledge into structured, statistically usable data.
Moderated teleconferences, workshops and live events bringing several experts to bear on a client's theme.
Facilitated plant tours, field research and in-person visits guided by domain experts.
Sourcing specialized experts, advisors and board candidates for client-specific needs.
Custom learning programs, executive mentorship and thought-leadership content for professional development.
GLG runs a two-sided marketplace. Clients pay membership or retainer fees for platform access and a set volume of expert interactions, with additional usage billed on top. Experts are compensated per engagement. GLG earns the spread between what clients pay for access and what experts are paid - and reinvests heavily in the matching, vetting and compliance machinery that makes the spread defensible.
That model has scaled to roughly $600M in annual revenue. GLG filed for a US IPO in 2021 seeking about $100M, then withdrew it in 2022 and remained private, backed by investors including Silver Lake, Bessemer Venture Partners and SFW Capital Partners.
Roughly a million experts across nearly every industry and geography - the largest single network in the category, which raises the odds of a precise match.
A screening and monitoring framework built for regulated clients. For finance and healthcare, that governance is often the deciding factor.
Not just calls - surveys, roundtables, site visits, events, recruitment and learning, so a client can move from one expert to structured data.
GLG competes with AlphaSights, Third Bridge, Guidepoint, Dialectica and Tegus - but it helped create the category they all operate in.
Where a management-consulting firm sells its own analysis and a data provider sells datasets, GLG sits one layer beneath both: it sells access to the raw human source. That makes it a supplier to consultants and investors as much as a competitor to them - a position at the base of the knowledge economy that is hard to dislodge.
Yale Law graduates Mark Gerson and Thomas Lehrman start Gerson Lehrman Group as a publisher of investor guidebooks.
Clients want to talk to the authors, not read the books. GLG drops publishing and begins selling subscriptions to its expert network.
GLG expands from finance into strategy consulting, life sciences, industrials and technology.
A pro-bono program begins connecting social-sector organizations with GLG's expertise.
Alexander Saint-Amand steps down after more than a decade; Paul Todd, formerly of eBay, becomes CEO.
GLG files for a ~$100M US IPO, then withdraws it and stays private.
Gemma Postlethwaite, a longtime board member and former Arizent CEO, takes over leadership of GLG.
Two Yale Law School graduates who founded GLG in 1998 and made the pivotal bet that human expertise, sold directly, was a business.
Former CEO of business-information firm Arizent, with leadership stints at Pira Energy and Thomson Reuters, now leading GLG's next chapter.
GLG's real expertise is organizational: building the systems to find, vet, match and compliantly deploy specialists at scale. The network spans finance, healthcare and life sciences, technology, industrials, energy, consumer goods, law and government - which is why a single client can run a semiconductor call in the morning and a drug-pricing survey in the afternoon.
GLG began by making guidebooks for institutional investors - then found its real business by watching how customers actually behaved.
The GLG wordmark and identity were created by Michael Bierut of Pentagram, one of the world's best-known graphic designers.
At roughly one million people, GLG's network is larger than the population of many major cities.
Alexander Saint-Amand, a former Bloomberg reporter, ran GLG as CEO for more than a decade until 2018.
It runs the world's largest expert network, connecting clients with vetted subject-matter experts through one-on-one calls, surveys, roundtables, site visits and custom research.
Hedge funds, private equity and asset managers, consulting firms, corporations across many industries, law firms and non-profits use GLG for fast primary-research insight.
It was founded in 1998 by Yale Law School graduates Mark Gerson and Thomas Lehrman, originally as a publisher before pivoting to expert consultations in 1999.
Roughly one million experts, making it the largest expert network in the world.
Gemma Postlethwaite became CEO in 2024, succeeding Paul Todd, who had led the company since 2018.
Profile compiled from public sources including Wikipedia, GLG's own sites and press coverage. Figures such as revenue (~$589M-$650M), employee count (~2,000-4,500) and expert-network size (~1M) are approximate and vary by source and year. Where a detail could not be verified it has been omitted.