Market intelligence · Partner economics
Partner Book of Business by Firm Tier
Reported partner books are not uniform across firm tiers, and the differences are systematic, not random. In our interviews with 2,600+ partners, Magic Circle USD books clustered with a median in the $4–6m band; US elite Am Law books centred tighter around $2.5–3.5m; boutique partners reported the widest spread relative to their median of any tier (a ~$2m median against a ceiling near $48m), with portability rates that outpaced every other category. The numbers matter less than what they reveal about how client ownership, firm platform, and rate structure combine to make a book portable — or not.
Pick a tier. Watch portability move — not book size.
A bigger book is not a more portable book. Choose a firm tier and the share of partners who call their own book highly portable swings from one in four to one in two.
Of portability-assessed boutique and specialist partners described their book as highly portable — the highest rate of any tier (30 of 59 assessed). Sartori Global databook
Magic Circle reports the highest USD median book and the lowest portability. Boutiques report a modest median and the highest portability. Size and portability are different axes. Every figure is in the table below.
What the numbers come from.
Every figure on this page is drawn from Sartori Global's proprietary interview corpus — not market surveys, not published league tables. The hedges are honest ones: this is our pipeline, not the whole market.
- ~2,667
- Partner-level conversations in Sartori Global's proprietary interview dataset — the source for every figure on this page.
- Sartori Global databook
- 400+
- Conversations in which portability was an explicit theme — the single most-discussed topic after compensation in partner lateral interviews.
- Sartori Global databook
- ~51%
- Of portability-assessed boutique and specialist firm partners described their book as highly portable — the highest rate of any firm tier in our dataset (assessed basis; 30 of 59 assessed).
- Sartori Global databook
- 85
- Conversations in which billing rate inflation risk was the explicit objection — the partner's client base built at rate levels the target firm cannot match.
- Sartori Global databook
The classification: four outcomes
Every book conversation on this page is filtered through one four-outcome classification. It runs from a relationship the partner owns to one the firm owns — left to right, the client follows the individual less and the firm more.
Partner owns the clientFirm owns the client
- 01 Highly portable The client follows the individual, not the firm brand. The relationship was personally sourced and travels with the partner.
- 02 Partially portable Mixed — some clients follow, some stay with the firm or reassess the relationship when the partner moves.
- 03 Low portability Work is panel-driven, institutional, or firm-relationship-dependent. Approved-vendor status and panel inertia do not travel.
- 04 Institutional The book effectively belongs to the firm, not the partner. The relationship is held by the platform, not the individual.
A book's size is the headline; its portability is the substance.
How do reported books differ across firm tiers?
The table below aggregates banded book ranges and portability profiles by firm tier. Tier is self-reported — it reflects the firm the partner was at or targeting, not a third-party ranking. Currencies are shown within-tier; figures are not cross-converted.
Across more than 700 partners for whom book data was captured, the tier breakdown reveals four distinct patterns: a high-ceiling Magic Circle cohort with significant institutional drag, a compact US elite cluster with stronger portability, a wide-range International category reflecting the heterogeneity of global platform firms, and a boutique segment where portability concentrations are the highest of any tier even as median books sit in the same band as US national firms.
From headline book to portable revenue
The number a partner reports is not the number a firm underwrites. Three deductions stand between a headline book and the revenue that actually arrives — and a higher tier does not shrink them.
What are the banded book ranges by firm tier?
| Firm tier | Currency | Reported range | Median band | Observations (n) |
|---|---|---|---|---|
| Magic Circle | USD | $0.2m – $51m+ | ~$4–6m | 34 |
| GBP | £1.6m – £20m | ~£3m | 13 | |
| EUR | €0.75m – €15.5m | ~€3–4m | 14 | |
| US Am Law (elite) | USD | $0.1m – $31.75m | ~$3m | 64 |
| US Am Law (other) | USD | $0.1m – $40m | ~$2m | 69 |
| International / Global | USD | $0.2m – $20m | ~$2m | 104 |
| EUR | €0.3m – €20m | ~€1.5–2m | 60 | |
| GBP | £0.14m – £15m | ~£1.85m | 41 | |
| Silver Circle | USD | $1m – $31m | ~$2.5m | 21 |
| GBP | £0.1m – £4.25m | ~£1.3m | 5 | |
| Boutique / Specialist | USD | $0.3m – $48.3m | ~$2m | 49 |
| GBP | £0.18m – £2m | ~£1m | 8 | |
| UK National / Top | GBP | £0.21m – £9m | ~£2m | 14 |
Three things stand out immediately. First, the ceiling matters as much as the median. Magic Circle USD books reach into the $50m-plus band because those platforms attract multi-jurisdictional, cross-practice mandates where origination credit spans a whole client relationship, not a single matter. Second, the boutique USD ceiling ($48m+) is comparably high despite a much lower median ($2m), which is a signature of the all-or- nothing concentration typical of specialist firms: most partners have modest books by practice breadth, but the outliers own a relationship entirely. Third, International/Global medians cluster tightly across currencies — the GBP, EUR and USD medians all sit in the £1.8m–$2.1m range, suggesting that the "global platform" tier is more internally consistent than the headline tier label implies.
Most partners have modest books by practice breadth, but the outliers own a relationship entirely.
How does portability differ across tiers?
A book's size is the headline; its portability is the substance. Across 700+ portability-assessed conversations in our dataset, the tier a partner comes from is one of the strongest predictors of how their book will be classified. Percentages below are assessed-basis (denominator = n assessed; excludes not-assessed conversations).
In our interviews with 2,600+ partners, portability was the single most-discussed substantive theme after compensation — featuring as an explicit topic in roughly 400 conversations. The classification we use covers four outcomes: highly portable (the client follows the individual), partially portable (some clients follow, some reassess), low portability (work is panel- or firm-relationship-driven), and institutional (book belongs to the firm). The table below shows how those categories distribute across the tiers in our dataset.
What is the portability breakdown for each firm tier?
| Firm tier | Total assessed (n) | Highly portable | Partially portable | Low portability | Institutional | Not assessed |
|---|---|---|---|---|---|---|
| Magic Circle | 70 | 14 (25%) | 30 (53%) | 8 (14%) | 5 (9%) | 13 |
| US Am Law (elite) | 70 | 29 (50%) | 24 (41%) | 4 (7%) | 1 (2%) | 12 |
| US Am Law (other) | 75 | 28 (44%) | 21 (33%) | 10 (16%) | 4 (6%) | 12 |
| International / Global | 227 | 86 (43%) | 92 (46%) | 19 (10%) | 2 (1%) | 28 |
| Silver Circle | 35 | 10 (43%) | 12 (52%) | 1 (4%) | 0 (0%) | 12 |
| Boutique / Specialist | 67 | 30 (51%) | 23 (39%) | 6 (10%) | 0 (0%) | 8 |
| UK National / Top | 19 | 5 (31%) | 8 (50%) | 3 (19%) | 0 (0%) | 3 |
The contrast between Magic Circle and US elite Am Law is the most instructive comparison in the table. Despite Magic Circle books reporting a higher median in USD terms, only 25% of Magic Circle partners in our dataset described their book as highly portable — compared to 50% of US elite Am Law partners. Magic Circle books were over twice as likely to carry an institutional or low-portability classification. That reflects the structural difference between lockstep platforms with deep client-relationship infrastructure (where the firm holds the relationship) and the eat-what-you-kill or modified-merit US model (where origination credit attaches to the individual).
Boutique and US elite Am Law firms lead the tier table on highly portable books (51% and 50% respectively on assessed basis), but for different reasons. Boutique portability is concentration-driven: the partner owns the client because they built the entire relationship personally, often without associate bench support. US elite Am Law portability reflects the origination-credit architecture of the US partnership model — partners at those firms are structurally incentivised to own client relationships in a way Magic Circle lockstep is not.
Size against portability: the two-axis read
The whole article in one frame. The vertical axis is reported median book; the horizontal axis is the highly-portable share. A higher tier buys a bigger median, not a more portable one — the two axes move independently.
The portability range across the table.
Magic Circle — lowest portability
The highest USD median book in the table, but the lowest share of partners who call their book highly portable (14 of 70 assessed).
Sartori Global databookWhich archetypes shape how book conversations go?
Book size and portability are the inputs. What happens in the lateral conversation is shaped by a smaller set of recurring patterns. In our dataset of 2,667 interviews, ten objection archetypes account for the great majority of deal-blocking moves.
Across roughly 2,789 classified objections in our dataset, three archetypes dominate and directly involve the book of business. The Client Portability Uncertainty archetype (198 conversations, 7.1% of classified objections) is the clearest: the partner cannot commit to bringing a portable book because institutional clients sit with the firm, work is panel-driven, or the reported book falls below the target firm's threshold. What makes this archetype distinctive is that it is not a negotiating position — it is a structural constraint. Panel relationships, approved-vendor status, and institutional client inertia cannot be talked around. The partner is describing a reality about client ownership, not a reluctance to move.
The Billing Rate Inflation Risk archetype (85 conversations, 3.0% of classified objections) is the second book-specific pattern. It emerges when a partner's client base was built at a lower rate structure and will not absorb the target firm's standard rates. In our interviews, this came up most frequently in disputes and litigation (20% of the archetype), corporate and M&A (15%), IP (8%), and projects and energy (8%). The issue is structural, not cosmetic: a book that is highly portable in principle becomes conditionally portable in practice if the rate differential is large enough to trigger client resistance. Rate grandfathering requests are common; they are not always granted.
The third book-adjacent archetype is Compensation Floor & Package Mismatch (156 conversations, 5.6% of classified). This one connects book to pay: partners with strong, genuinely portable books frequently use that strength as a floor in compensation negotiations, stating explicitly that they will not move for less than current equity plus bonus. When the target firm's offer falls short of that floor, the book — however large — does not close the gap.
Which objection archetypes most directly involve the book of business?
| Archetype | Conversations (n) | % of classified | Top practices |
|---|---|---|---|
| Client Portability Uncertainty | 198 | 7.1% | Disputes 22%, Corporate/M&A 12%, Banking & Finance 7% |
| Compensation Floor & Package Mismatch | 156 | 5.6% | Disputes 22%, Corporate/M&A 21%, Projects/Energy 7% |
| Billing Rate Inflation Risk | 85 | 3.0% | Disputes 20%, Corporate/M&A 15%, IP 8% |
| Associate Bench & Practice Infrastructure Gap | 252 | 9.0% | Capital Markets 13%, Corporate/M&A 12%, Projects/Energy 11% |
| Platform & Brand Downgrade | 399 | 14.3% | Corporate/M&A 14%, Disputes 12%, Banking & Finance 9% |
Two of these archetypes — Associate Bench & Practice Infrastructure Gap and Platform & Brand Downgrade — are not primarily about the partner's own book but about the receiving firm's ability to service it. Partners with large, complex books (particularly in capital markets, corporate, and projects/energy/infrastructure) raised the bench depth problem in 252 conversations: a solo hire without associate depth cannot run mega-deals; a 26-lawyer office with 14 partners to 3 associates cannot absorb a practice that requires four to six partners and ten to fifteen associates per deal. The brand downgrade objection (399 conversations, the second most common in the entire dataset) connects book risk to firm prestige: a partner moving to a platform perceived as inferior faces the real possibility that institutional clients use the move as an opportunity to reassess the relationship.
A USD $10m book that sits on a panel may generate a weaker offer than a USD $4m book that is wholly personally sourced.
What does the tier gap mean for a partner considering a move?
The book data across tiers points to a specific tension that recurs in lateral negotiations: a higher-tier book is not automatically more portable, and a more portable book is not automatically larger. Understanding which constraint binds first determines how a move gets structured.
In our interviews, the partners who navigated this tension most cleanly were those who had done their own honest portability assessment before the first conversation with a potential firm — not after. The question is not “how much do I bill?” but “how much would follow me, at what rate, and over what timeline?” Those are three separate questions, and the answers interact.
For Magic Circle partners, the honest answer to the first question often involves distinguishing between the institutional layer of the book (which stays with the firm) and the personal relationship layer (which may be portable). In our conversations, Magic Circle partners in the highest-portability bracket described books that were built on personal origination — often in a practice or market where the partner was effectively the firm's entry point for a client type, not a beneficiary of existing firm-brand pull. The institutional drag was real but bounded.
For boutique partners, the portability strength is genuine but the infrastructure question is the binding constraint in the opposite direction. Across 2,600+ conversations, the Platform Scale Constraint motivation archetype was the most common driver of movement (815 conversations, 25.1% of classified motivations): current firm structurally caps practice growth through inadequate staffing, rate ceilings, or an infrastructure too thin for the book the partner is building. The boutique partner with a highly portable $5m–$8m book who cannot grow further without a larger associate bench is the canonical version of this archetype. Moving up-market is the right call structurally; the challenge is that the move also reprices the book upward, which is why the billing rate inflation risk archetype overlaps disproportionately with disputes and transactional boutique practices.
How do top motivations connect to firm tier and book dynamics?
| Motivation archetype | Conversations (n) | % of classified | Primary tier connection |
|---|---|---|---|
| Platform Scale Constraint | 815 | 25.1% | Boutique / US national — book outgrows the platform |
| Passive Market Listener | 693 | 21.3% | All tiers — keeping optionality open without urgency |
| Geographic Platform Gap | 339 | 10.4% | International / Global — cross-border client needs |
| Culture & Autonomy Deficit | 310 | 9.5% | Magic Circle / lockstep — model friction with high originators |
| Compensation Undervaluation | 155 | 4.8% | All tiers — book growth not reflected in compensation |
| Compensation Model Mismatch | 56 | 1.7% | Magic Circle — lockstep undervaluing high originators |
The Culture & Autonomy Deficit archetype (310 conversations) surfaces disproportionately in Magic Circle contexts — and its connection to book dynamics is structural. When a partner generates materially more than lockstep bands reward, the conversation about moving is not purely about money but about whether the current model is the right vehicle for the book they are building. Partners in this cohort described frustration with eat-what-you-kill framing as frequently as the inverse: in our dataset, some wanted a collaborative model (and rejected US firms for that reason), while others explicitly sought performance-linked rewards. The book is the same; the compensation architecture preference is the variable.
What should a hiring firm know before setting a portability threshold?
Firms that set book-of-business thresholds without adjusting for tier, practice, and rate compatibility are pricing themselves out of the candidates they most need — and retaining candidates whose books will not move even if the partner does.
The portability data across 700+ conversations suggests three things that should inform how firms calibrate lateral partner due diligence.
Do the honest assessment before the first conversation, not after. Three questions, in order.
| Question | Why it binds |
|---|---|
| How much of the book would actually follow me? | Institutional and panel layers stay with the firm — separate them honestly |
| At what rate will it follow? | A book built at lower rates is only conditionally portable at the target firm's pricing |
| Over what timeline does it migrate? | Portable revenue arrives on a schedule, not on day one |
| Is my book size or my portability the binding constraint? | A higher-tier book is not automatically more portable; a more portable book is not automatically larger |
| Does my book outgrow my current platform? | Platform Scale Constraint (815 conversations) was the most common driver of movement |
A single portability threshold across tiers is a calibration error. Three corrections.
| Correction | What the data shows |
|---|---|
| Tier is a portability proxy | A Magic Circle GBP 3m book may bring less than a boutique USD 3m book — higher institutional drag by construction |
| Rate compatibility is hidden portability | 85 conversations made billing-rate inflation the explicit deal-killer; grandfathered rates extract more portable revenue |
| Infrastructure runs both ways | 252 conversations blocked on the receiving firm's inability to execute — a USD 10m capital-markets book needs a team |
| Threshold without execution fails | Attract a large book without the bench to service it and the relationship migrates again within 18 months |
First, tier is a portability proxy, not a book-size proxy. A Magic Circle partner with a GBP 3m median book may bring less revenue than a boutique partner with a USD 3m median book, because the Magic Circle book carries a higher institutional drag by construction. Setting a single portability threshold across tiers produces systematic bias against large-platform partners whose books are structurally less portable but whose platform value — in relationships, reputation, and deal-quality signalling — is not captured by a raw book figure.
Second, rate compatibility is a hidden portability variable. In 85 conversations in our dataset, billing rate inflation risk was the explicit deal-killer. A book that is highly portable at the current firm's rate structure may be only partially portable at the target firm's rates. Firms that offer grandfathered client rates during a transition period extract meaningfully more portable revenue from lateral moves. Firms that enforce standard rates immediately compress the effective portability of the book.
Third, the infrastructure question runs in both directions. Across the Associate Bench & Infrastructure Gap archetype (252 conversations), the blocking factor was not the partner's book but the receiving firm's inability to execute it. A USD 10m book in capital markets requires a team. Setting a threshold that attracts large-book partners without building the execution infrastructure to service their client base is a formula for lateral failure on both sides. The firm gets the partner; the partner's clients do not get the work done at the standard they expect; the relationship migrates again within 18 months.
Tier is a portability proxy, not a book-size proxy.
Every figure here traces to our proprietary databook and its methodology.
Sources & companion analyses
8 references- Sartori Global — Our Methodology server.sartoriglobal.com ↗
- What Book of Business Portability Means server.sartoriglobal.com ↗
- Partner Book of Business by Practice server.sartoriglobal.com ↗
- Partner Book of Business by Market server.sartoriglobal.com ↗
- What Partners Really Make at the Top Am Law Firms server.sartoriglobal.com ↗
- What Partners Really Make in London Law Firms server.sartoriglobal.com ↗
- Lateral Partner Hiring server.sartoriglobal.com ↗
- Associate Rates Leaked: What Court Filings Reveal server.sartoriglobal.com ↗
Every figure on this page is a banded aggregate from Sartori Global's proprietary interview dataset of ~2,667 partner-level conversations. No figure is traceable to an individual lawyer or a specific firm; tier labels are self-reported; currencies are not cross-converted. See our methodology for sample construction, survivorship bias, and classification.
Keep reading
What Partners Really Make at the Top Am Law Firms
The compensation architecture behind the book figures — how origination credit, equity bands, and lockstep versus merit models translate reported books into take-home pay.
Read partner pay at the Am Law top 50What Partners Really Make in London Law Firms
The UK equivalent — how Magic Circle lockstep, Silver Circle merit, and US-firm lateral guarantees translate the GBP book figures into partner compensation.
Read London partner payLateral Partner Hiring
How firms structure, diligence, and integrate partner laterals — the process behind the portability assessments and book conversations in our dataset.
Read the lateral hiring guideAssociate Rates Leaked: What Court Filings Reveal
The rate card that sits beneath every book-of-business conversation — what elite firms actually bill and why billing rate inflation risk is a structural partner mobility constraint.
Read the associate rate analysisOur Methodology
How we build and interpret our proprietary interview dataset — sample construction, survivorship bias, currency conventions, and classification methodology.
Read our methodologyWork with Sartori & Partners
Whether you are a law firm building a practice or a senior lawyer mapping your options, our research desk works from the same dataset that underlies this analysis.
Get in touchPartner book of business: common questions
How large are reported partner books at Magic Circle firms compared with US elite Am Law firms?
In our conversations with 70+ partners at Magic Circle firms, USD-denominated books ran from under $1m to just over $50m, with a median in the USD $4–6m band. GBP-denominated books from the same cohort had a median around £3m. Across 70+ partners at US elite Am Law firms, USD books showed a tighter central cluster with a median around USD $2.5–3.5m. The Magic Circle USD median is notably higher, but the currencies differ and the dataset skews toward candidates actively in a lateral conversation — it does not represent the full partnership. Portability profiles also diverge sharply: Magic Circle books were more likely to be classified as partially portable or institutional, whereas US elite Am Law partners leaned toward highly portable or partially portable.
Why do boutique and specialist firm partners sometimes report books as large as those at global firms?
Across 67+ partners at boutique and specialist firms in our dataset, USD-denominated books ranged from under $1m to nearly $50m, with a median around USD $2m. The wide ceiling reflects that boutique partners often own a concentrated, personally sourced client relationship — there is no firm brand absorbing origination credit. That same concentration is why portability at boutiques skewed heavily toward highly portable: roughly 51% of portability-assessed boutique partners described their book as highly portable (30 of 59 assessed), the highest rate of any tier. The trade-off is infrastructure: those books are portable precisely because they were built without associate bench depth or cross-practice referral feed, which also caps how large the median can grow.
What does portability actually mean in a lateral partner conversation, and how is it assessed?
Portability is how a partner characterises the likelihood that their clients will follow them to a new firm. In our interview process we classify it across four outcomes: highly portable (client follows the individual, not the firm brand), partially portable (mixed — some clients follow, some stay with the firm or reassess), low portability (work is panel-driven, institutional, or firm-relationship-dependent), and institutional (book effectively belongs to the firm, not the partner). Across more than 2,600 partner conversations, portability emerged as the single most-discussed theme after compensation — it featured in roughly 400 explicit conversations. The classification is the partner's own assessment, shaped under interview conditions; it is not a verified post-move outcome.
Which practices tend to have the least portable books, and why?
Disputes and litigation partners showed the widest portability spread of any practice in our dataset: across 153 portability-assessed conversations, roughly 29% were classified as low portability (44/153, among partners whose book portability we assessed) and another 39% as partially portable (59/153, among partners whose book portability we assessed) — one of the higher combined low-and-institutional shares among the larger practice cohorts. The primary driver, cited repeatedly in the Client Portability Uncertainty archetype (198 conversations), is that major institutional litigation clients follow approved panels and firm relationships, not individual partners. Arbitration showed a similar pattern. Capital markets partners also skewed toward partially portable (60% partially portable on assessed basis), driven by panel-dependency on the lender or underwriter side. Banking and finance partners, by contrast, leaned toward highly portable (43% highly portable vs 38% partially portable on assessed basis), reflecting more personal-relationship-driven mandates. Regulatory, insurance, and restructuring partners similarly showed higher rates of high portability — the client relationship in those practices is often built on a specialist personal reputation rather than a firm-brand mandate.
Does a larger book of business always translate to a stronger lateral offer?
Not automatically. Across more than 2,600 conversations in our dataset, the most common book-related objection blocking a lateral move was not book size but portability uncertainty — featured in 198 explicit conversations (the largest of the three book-specific archetypes: 198 vs Compensation Floor 156 vs Billing Rate 85) and underpinning several of the largest archetypes. A USD $10m book that sits on a panel or institutional client relationship may generate a weaker offer than a USD $4m book that is wholly personally sourced and demonstrably portable. Hiring firms diligence the revenue that will actually arrive, not the headline number. The second major constraint is rate compatibility: 85 conversations across our dataset surfaced the billing rate inflation risk archetype — partners whose client base was built at lower rate structures that cannot absorb the target firm's standard pricing, making the nominal book conditionally portable at best.
The market read behind the numbers
Mapping a lateral move or a partner hire? Start with the real book conversation.
Our dataset covers 2,600+ partner conversations. Whether you are a law firm setting a portability threshold or a partner assessing how your book will travel, we can give you the read that the public data cannot.