Bill Achtmeyer, Founder of The Parthenon Group, Joins Matters Graph as Chairman of Its Advisory Board

Achtmeyer, who grew Parthenon from two partners into what became EY-Parthenon’s 5,000-consultant practice, joins the founders of a buy-side specialist built in Parthenon’s tradition, to help scale the firm as a record exit backlog puts underwriting under scrutiny

WASHINGTON--(BUSINESS WIRE)--Bill Achtmeyer, founder of The Parthenon Group, has joined Matters Graph^® as Chairman of its Advisory Board, working alongside Mark Stein and Jeff Merkle, who founded the firm in 2017. Matters Graph is a strategy consulting firm that serves private equity sponsors, private credit, and corporate development teams. It has deliberately limited its work to two things: commercial due diligence for buyers and commercial value creation for the businesses its clients own. It does no sell-side work.

Achtmeyer joined Bain & Company in 1977 and rose within 14 years to be one of the firm’s 10 Senior Partners, and founded Bain’s mergers and acquisitions practice. In 1991 he founded The Parthenon Group, and over 23 years he grew it from two partners into a firm with nearly $100 million in revenue before its 2014 combination with EY. Achtmeyer then led EY-Parthenon through 2019 as it grew to $2 billion in revenue, 500 partners, and 5,000 consultants. EY kept the Parthenon name, which 12 years later still anchors EY’s strategy practice worldwide. That kind of name retention is rare when consulting firms are acquired, and it stands as a testament to the enduring qualities of the firm he built and led. In 2021 Achtmeyer co-founded Acropolis Advisors, a CEO advisory firm, with Harvard Business School professor and icon Michael Porter.

From Parthenon’s founding in 1991 until its combination with EY in 2014, leading private equity and corporate M&A houses had two primary firms they called first when an investment case had to be examined: Bain & Company and The Parthenon Group. Over those same years, private equity grew into the largest buyer of companies in the economy, but the number of firms built for buy-side diligence did not grow with it. Stein and Merkle founded Matters Graph to fill that gap. Of the strategy firms serving the largest U.S. sponsors and lenders, Matters Graph is one of only two that work entirely on the buy side; the other is Bain. Matters Graph is also, by intent, the only one with no other lines of business: a specialist designed wholly around the fundamentals of an investment case and the investor it serves, with no reason to tell a buyer what a seller wants to hear. As the firm enters its second decade, Achtmeyer joins to help shape and lead its plan to grow the partner base and reach its own $100 million benchmark.

“I am honored to join Matters Graph as the inaugural Chairman of its Advisory Board. Mark Stein, the firm’s Co-Founder and Senior Partner, is someone I had the opportunity to meet through a former member of my Parthenon team. He and his partner, Jeff Merkle, have built something very special, and it reminds me of when I began the M&A practice at Bain & Company and the private equity practice at The Parthenon Group,” said Bill Achtmeyer. “Both of those practices have become world-renowned. What distinguishes Mark, Jeff, and their team is their focus on two critical elements in the private equity commercial due diligence world. First, they do only buy-side work. Second, they focus their work on the acquisition target’s customers. They do not rely on expert groups. They do not rubber-stamp the investment thesis of the deal team. They act, as all consultants should, as objective arbiters. As in the famous catchphrase of Sgt. Joe Friday of Dragnet, ‘All we want are the facts.’ Consequently, they have already built an enviable private equity clientele of both large and midsize firms in the U.S., and their reputation is beginning to blossom. These folks are the real deal and have enormous growth potential. I intend to engage them when we are advising our CEO clients on deals and expect that they will make a large impact on a profession that seems intent on serving sellers rather than buyers.”

The announcement comes as the private equity industry holds the largest backlog of unsold companies in its history, a condition The Wall Street Journal, Bloomberg, and the Financial Times have each reported this year. Bain & Company’s 2026 Global Private Equity Report puts that backlog at some 32,000 buyout-backed companies worth about $3.8 trillion, with holding periods near seven years. The industry’s growth helps explain it: assets managed by private equity firms worldwide rose from roughly $650 billion in 2000 to an estimated $10.5 trillion in 2024, according to KKR, and the American Investment Council counts around 6,000 private equity firms headquartered in the U.S. today. The Bain report also finds that the annual EBITDA growth a buyout now needs to earn its return has more than doubled, from approximately 5% to 12%. And EY’s Q1 2026 Private Equity Pulse finds that 60% of private equity firms are expanding their commercial diligence.

Matters Graph holds the view that a large share of this backlog, and of the portfolio underperformance beneath it, traces to diligence that held a weak mandate. Poor diligence weakens the investment decision and the underwriting behind it, so that neither holds up under its base and downside cases. The result is companies bought at prices that assumed growth and value creation plans no one had rigorously tested with the customers who would have to deliver them. The firm’s long-held premise is that the return on an acquisition is set at the purchase, and that the growth in a thesis either exists in those customers or it does not. Sponsors tell the firm as much: the decks they have been conditioned to accept are, in their words, “all too often simply positive and up and to the right,” regardless of what a proper investigation would have uncovered, and without the insight needed to inform underwriting or a value creation plan. Too many of today’s decks, they say, are plainly perfunctory. Matters Graph’s entire design is to help investors win the exit by winning the acquisition decision, not the bid. The investment committee vote is a checkpoint, not the goal, and the work is judged on the outcome and the strength of the portfolio.

“A deck can’t crack a case that was tested only lightly,” said Mark Stein, Co-Founder and Senior Partner. “We write the thesis first and then test it rigorously, with extensive investigative primary research coupled with only sound, hard external data, focused on the few questions the return depends on. Testing is only half the work. The other half is discovery: finding the latent and intrinsic value in a business and its market that the thesis has not yet counted, because that is where the returns beyond the plan come from. The evidence carries the thesis, breaks it, or sometimes improves it. We’re stubborn about this on purpose. The capability we’ve built is diligence that carries the hold, not just the investment committee decision.”

Because an investment thesis is a prediction about what customers will do, and therefore about future cash flows, Matters Graph treats customers as the most valid source of primary evidence. The firm refuses to use expert networks or panels, and it takes a deep investigative approach to the intent and behavior of current, prospective, and lost customers, probing four levels down to determine where a market and its behaviorally defined segments are headed and what a company and a thesis are positioned to achieve.

“The people who know whether a business will grow are its customers and the channel that sells it: the customers it has, the ones it lost, and the ones who chose someone else,” said Jeff Merkle, Co-Founder and Senior Partner. “We interview them in volume and by role to find the segments that will carry the thesis and the ones that will sink the deal.”

Achtmeyer, Stein, Merkle, and the management team will work together on the firm’s next stages of growth, including the governance and leadership bench a larger firm needs; the senior team; the firm’s codified standard work, best practices, and published research; and its relationships with sponsors, private credit, and corporate acquirers, across their investment and value creation teams.

“Bill rose to the senior leadership of Bain and then built one of the two firms that defined this field,” said Stein. “Growing a professional services firm well is its own discipline, and Bill has done it twice, first at The Parthenon Group, from two to 28 partners and 350 team members, and then at EY-Parthenon, which reached 500 partners and 5,000 consultants, with the economics, the people, the path to partner, and the standard of the work all holding at once. Bill and I have become fast friends over the past two years, and he has come to know our firm from the inside. Chairing our Advisory Board is a different order of commitment, and he was the first and only person we wanted for it. He joins on the same terms as the people who scale the firm, under an ownership program that, as far as we know, makes us the first strategy consulting firm to adopt the broad-based ownership model that private equity has increasingly used for its portfolio companies.”

About Bill Achtmeyer

Bill Achtmeyer joined Bain & Company in 1977 and rose within 14 years to be one of the firm’s 10 Senior Partners, and founded Bain’s mergers and acquisitions practice. He founded The Parthenon Group in 1991 and led it, and then EY-Parthenon, for 28 years. He is the co-founder of Acropolis Advisors, a CEO advisory firm, and has advised chief executives at Ford Motor Company, Corning, eBay, Herman Miller, Starwood Hotels & Resorts, and Thomson Reuters. He has served as board chair of the Boston Symphony Orchestra and the Massachusetts High Technology Council, and as chair of the Board of Advisors of Dartmouth’s Tuck School of Business. He holds an A.B. from Princeton University and an M.B.A. from Tuck.

About Matters Graph

Matters Graph^® is a buy-side-only commercial due diligence and value creation specialist and, to its knowledge, the only firm serving the largest U.S. sponsors and lenders at scale that is devoted to this work alone. Founded in 2017 and headquartered in Washington, D.C., it serves private equity sponsors, private credit, and corporate development teams in North America and Europe. It does no sell-side work and builds its analysis on investigative Voice of Customer and Voice of Channel research with the customers of the businesses under study. For more information, visit www.MattersGraph.com.