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COGNITIVE SERVICES
Accounting / Audit
Leader: Deloitte — 7.9% S1 · 18.7% CR3
S1
leader
CR3
top 3 combined
HHI
Unconcentrated
MARKET SIZE
US
How this is calculated
FORMULA
S1 = Deloitte revenue / total revenue = 7.9%
CR3 = Deloitte + PwC + EY = 18.7%
HHI = Σ(share²) = 130 (Unconcentrated (HHI < 1,500))
DENOMINATOR
Revenue — $420B (US)
Total US professional services market: combined US accounting/audit/tax services (NAICS 5412, ~$210B) plus US management consulting services (NAICS 5416, ~$210B). Broader than NAICS 5412 alone because Big 4 firms publicly disclose only full-firm US revenue (which spans audit + tax + advisory + consulting), so the denominator must match that scope.
Size from: IBISWorld NAICS 5412 + 5416
TOP 3 PLAYERS
#1Deloitte7.9%
#2PwC5.4%
#3EY5.4%
METHODOLOGY NOTE
Deloitte LLP US FY24 revenue ~$33.0B, PwC US ~$22.75B, EY US ~$22.7B (firm press releases). Divided by combined US accounting + management-consulting market (~$420B; NAICS 5412 + 5416 per IBISWorld). Methodology fix Nov 2025: prior version divided full Big 4 firm revenue (which includes consulting) by NAICS 5412 alone (which excludes consulting), inflating shares — apples-to-oranges. The broader denominator captures the actual scope of Big 4 work and yields more honest CR3 of ~19%. KPMG US ~$13B is a near-tie #4 (would push CR4 to ~22%). For SEC issuer audit specifically the picture is far more concentrated (Big 4 audit ~99.7% of S&P 500 by fees per Audit Analytics) — that would be a separate sub-market.
Year: 2025
Geo: US
Firms: 50,000+
NAICS: 5412 + 5416
Historical S1 / CR3 trajectory
1960S1: 12.5%CR3: 37%Big 8 era
1980S1: 14%CR3: 40%Big 8 growing
1989S1: 18%CR3: 50%Big 8 → Big 6
1998S1: 22%CR3: 60%Big 6 → Big 5 (PwC)
2002S1: 28%CR3: 75%Big 5 → Big 4 (Andersen collapse)
2010S1: 20%CR3: 52%Advisory dilutes share
2025S1: 7.9%CR3: 18.7%Big 4 stable; broader denominator (5412+5416)
Labor economics
REV / EMPLOYEE (leader)
$0.4M
industry avg $0.3M
SG&A % (leader)
40%
of revenue
Deloitte (private global verein) — SG&A unverified; 40% is directional estimate
Related markets
Source Quality Hierarchy
Every market has a primary source plus 1–3 validation sources. Revenue numerators come from SEC 10-K filings; denominators validated against the Economic Census where available.
TIER 1Authoritative anchorsGovernment data + SEC filings
US Economic Census (data.census.gov) · SEC EDGAR / Company 10-Ks · BEA Industry Value-Added (FRED) · BLS QCEW · USGS Mineral Commodity Summaries · EIA Refinery Capacity Report · FDA device listings
TIER 2Leading commercial trackersIndustry-standard paid trackers
IDC Semiannual Software Tracker · Gartner Market Share & Magic Quadrant · IBISWorld NAICS reports · StatCounter Global Stats · eMarketer / Insider Intelligence · Synergy Research Group
TIER 3Category specialistsBest-in-class niche authorities
SIPRI (aerospace & defense) · IQVIA (pharma) · TrendForce (semiconductors) · CIMdata (CAD/PLM) · Nilson Report (payments) · Am Law 100 (legal) · ENR Top 500 (A&E) · AM Best (insurance) · SIA (staffing) · Ad Age (agencies) · Barron's / Cerulli (wealth) · Evaluate MedTech · Nielsen Gauge (streaming) · Gridwise (ride-hail) · Bloomberg Second Measure (delivery) · RC Top 100 (roofing) · SDM Top 100 (fire/safety) · Big 4 annual reports · ALM Intelligence (consulting)
Data vintage: Q2 2025 research compilation. Labels updated 2026-Q2. Tier 1 sources refreshed from FY2025 SEC filings where available. For full methodology see the Methodology page.