202608 Concentration: Top-1 Holds 28% of Big-5 AI Capex — Top-3 Holds 74%
Late-Aug 202608 concentration lens on the Big-5 stack (~$858B): Amazon alone is 28%; Amazon+Alphabet+Microsoft hold 73.8%. HHI ≈ 2,227. Q3→202608 raises are even more skewed — Amazon+Alphabet capture ~78% of positive dollar raises.
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Absolute AI infrastructure dollar totals answer how large is the stack. They do not answer how concentrated is the system at the top of the distribution. That is the capital-markets question this late-Aug 202608 concentration lens is built for.
Our theme already maps the vintage path: the July research spend map put Big-5 midpoints near $760B; the Aug post-Q2 update revised to about $802.5B; the mid-Q3 spend update printed roughly $835B; and the late-Aug 202608 spend update now sits near $858B. The Q3 concentration companion answered the distribution question on the mid-Q3 tape. This post re-asks the same core question on the late-Aug 202608 desk vintage — so shares and levels stay on one tape with the newest absolute-dollar print.
The interactive dashboard above is a concentration lens, not another KPI strip. Top-1 share is 28.0% (Amazon, ~$240B). Top-3 share is 73.8% (Amazon + Alphabet + Microsoft, ~$633B of ~$858B). Approximate Big-5 HHI is ~2,227 — elevated versus a five-way equal split (~2,000). Pair this distribution cut with the intensity / cash-flow frame for affordability, and with the absolute-dollar updates for the vintage path.
The 202608 concentration scoreboard
| Metric | Value | Why it matters |
|---|---|---|
| Big-5 late-Aug 202608 midpoint sum | ~$858B | Concentration perimeter for this post |
| Top-1 share (Amazon) | 28.0% | Single-name program risk in the stack |
| Top-1 dollars | ~$240B | Larger than many entire industry cohorts |
| Top-3 share (AMZN+GOOG+MSFT) | 73.8% | Three firms hold roughly three-quarters |
| Top-3 dollars | ~$633B | Rest of Big-5 is a minority slice |
| Approximate Big-5 HHI | ~2,227 | Above equal-split HHI of 2,000 |
| Mid-Q3 → 202608 raise | +$23B | How the stack moved from $835B |
| Amazon+Alphabet share of positive raises | ~78% | Growth concentration exceeds stock concentration |
| AI-attributed slice (~75% convention) | ~$644B | Scope toggle — not a 10-K line |
Read the table as a ladder. Absolute dollars rose nearly fourfold from 2024 (~$231B) to late-Aug 2026 (~$858B). Concentration did not equalise. Top-1 share drifted from the low thirties toward the mid-twenties in July research, then re-concentrated as Amazon’s late-Aug raise reclaimed share. Top-3 stayed in a tight band around the mid-to-high seventies — a larger oligopoly, not a broad industrial base.
Top-1 and top-3: the late-Aug company ladder
On the late-Aug 202608 vintage the ranked Big-5 ladder is:
- Amazon — $240B (28.0%)
- Alphabet — $218B (25.4%)
- Microsoft — $175B accounting CY (20.4%)
- Meta — $150B (17.5%)
- Oracle — $75B net of prepayments (8.7%)
Cumulative share hits 53% after two names and 74% after three. That is the visual the Lorenz panel is built to show: the equal-split diagonal is a straight 20/40/60/80/100 path; the actual path bends hard toward the top-left.
Two definition notes matter immediately. Microsoft’s $175B is the accounting calendar print after lease reclassification — economic campus spend is still commonly modeled nearer ~$190B. Toggle the Microsoft control in the dashboard: under the economic frame, top-1 eases slightly to ~27.5%, top-3 edges to ~74.2%, and the Big-5 sum moves to ~$873B. Oracle’s $75B is net of customer prepayments; gross cash outlays remain nearer $95–100B. Neither caveat erases the concentration story. Both change the second decimal, not the shape of the ladder.
Alphabet’s second-place share is itself a concentration signal. Four guidance raises in a calendar year — from the low-$180Bs toward a $210–225B band with midpoint $218B — mean the number-two program is not a static runner-up. It is a rising second pole. Amazon and Alphabet together hold ~53% of the late-Aug stack before Microsoft is even counted.
Compared with the mid-Q3 concentration companion, Amazon’s share stepped from 27.5% to 28.0% and HHI from roughly 2,211 to 2,227 on a hotter stack. The direction is re-tightening at the top, not equalisation.
Growth is more concentrated than the stock
Stock concentration (who holds today’s dollars) and raise concentration (who captured the Q3→202608 path) are related but not identical. From the mid-Q3 print (~$835B) to late-Aug (~$858B), the Big-5 midpoint sum rose about +$23B / +2.8%.
Decompose the positive company raises and the picture skews further:
- Amazon +$10B
- Alphabet +$8B
- Meta +$5B
- Oracle $0 (net-of-prepay flat)
- Microsoft $0 (accounting print flatlease reclass still the economic story)
Amazon + Alphabet alone account for roughly 78% of positive dollar raises. The donut panel makes that explicit: incremental authorizations on this step are more oligopolistic than the already-concentrated stock. For equity and credit desks that treat “the AI capex cycle” as a diversified industry factor, that raise skew is the practical rebuttal. Factor exposure is not five equal names — it is two programs doing most of the upward rewriting on the latest vintage step, with Microsoft and Oracle flat on the accounting / net prints while Amazon reclaims share.
Compared with the Aug→Q3 step — where Amazon+Alphabet captured about three-fifths of a larger positive raise pool — the Q3→202608 step is smaller in dollars but more top-heavy. Meta absorbs a real minority of the positive delta; Microsoft and Oracle contribute none on this step’s headline prints. That is why raise concentration can exceed stock concentration even when the absolute vintage delta looks modest.
Multi-year path: dollars up, equalisation incomplete
Track top-1 and top-3 across vintages:
| Vintage | Big-5 total | Top-1 share | Top-3 share | HHI (approx.) |
|---|---|---|---|---|
| 2024 actual | ~$231B | ~32.5% | ~79% | Elevated |
| 2025 actual | ~$344B | ~30% | ~77% | Elevated |
| 2026 Jul research | ~$760B | ~26% | ~76% | Softened |
| 2026 Aug post-Q2 | ~$802.5B | ~27.4% | ~74% | Re-tightened |
| 2026 mid-Q3 | ~$835B | ~27.5% | ~74% | Still elevated |
| 2026 late-Aug 202608 | ~$858B | ~28.0% | ~74% | Re-tightened again |
Two readings sit in that table. First, as more names authorized mega-programs (Oracle’s step-up; Meta’s band; Alphabet’s serial raises), top-1 share briefly eased even as top-1 dollars exploded — Amazon went from $75B (2024) to $240B (late-Aug) while its percentage of a much larger pie fell then recovered. Second, top-3 never left the mid-to-high seventies. The system did not become a broad industrial spend base; it became a larger oligopoly.
HHI on five Big-5 buckets stays above the equal-split benchmark of 2,000. That is a useful cross-post ranking tool, not a reconstructed global IT-capex census. The dual-axis panel — stack size rising while top-1 share stays sticky — is the capital-markets takeaway: scale and concentration can rise together.
From Jul research (~$760B) through late-Aug 202608 (~$858B), the cumulative raise is about +$98B / +12.9%. Shares moved less than levels on the long path, then re-concentrated on the latest step. That is the 202608 punchline in one sentence: the pie grew another $23B; Amazon and Alphabet wrote most of the rewrite.
Perimeters: when shares do not travel
Company shares only travel inside a declared perimeter. The dashboard’s perimeter bars put late-Aug Big-5 (~$858B) next to Street (~$845B), CreditSights (~$850B), GS Global Institute all-in AI infra (~$765B), and GS Investment Research hyperscaler (~$815B). Those houses are answering related but non-identical questions.
- Big-5 / Street / Credit are roughly company-gross hyperscaler worldsshare math is meaningful.
- GS GI is an all-in AI infrastructure construct (compute + data center + power). You cannot allocate that total into Amazon/Alphabet/Microsoft shares without inventing a mapping the institute did not publish.
- GS IR is a hyperscaler research path that can sit above or beside GI depending on year and bull/baseanother reminder that “AI capex” is a family of stacks, not one ticker.
Apply the CreditSights-style ~75% AI-attributed haircut and the AI-specific slice of the late-Aug Big-5 stack is about $644B. Toggle it in the ladder view so both perimeters stay visible. Treat the haircut as a convention for comparing AI-heavy programs, not as a disclosed segment line.
Street still trails the desk midpoint stack on this vintage (~$845B vs ~$858B). That gap is a timing artifact as much as a disagreement: consensus catches official raises with a lag. Concentration shares computed on the desk ladder can look slightly different from shares implied by a lagging Street sum — another reason to declare the perimeter before quoting top-1 / top-3.
What would change the concentration story
Several shifts would rewrite this scoreboard:
- A sustained non-Amazon top-1Alphabet or Microsoft clearing Amazon on a like-for-like gross (or economic) basis for consecutive vintages.
- Top-3 share falling through the low-sixties while the Big-5 total still growsevidence that Meta and Oracle (or a sixth hyperscaler-scale program) are absorbing incremental dollars faster than the top three.
- HHI drifting toward ~2,000 and staying there as the stack scalesequalisation, not just temporary raise noise.
- Raise concentration cooling so Amazon+Alphabet no longer capture roughly four-fifths of positive vintage deltas on a late-step refresh.
- Meaningful spend outside the Big-5 perimeter that makes “Big-5 share of AI infra” itself a falling metricsovereign, neocloud, and enterprise build-outs large enough to move the industry distribution, not just the footnotes.
None of those are guaranteed by another earnings-week raise. They are competitive and financing outcomes. Until they arrive, desks should price AI infrastructure risk as concentrated program risk first and diversified sector beta second.
Caveats and reading notes
- Perimeter is Big-5 hyperscaler gross midpoints (with Oracle net-of-prepay as disclosed). This is not a full global AI-infrastructure census and excludes large non-hyperscaler and sovereign programs.
- Microsoft lease reclassification moves dollars off the capex line without canceling servers or campusesuse the accounting/economic toggle rather than treating a flat headline as a build pause.
- Oracle net vs gross and Meta finance-lease principal affect levels; they do not invert the top-1 / top-3 ranking on current vintages.
- HHI is computed on five company buckets inside the Big-5 setuseful for ranking concentration across theme posts, not a plant-level market definition.
- AI-attributed ~75% is a CreditSights-style convention applied uniformly; company-level AI mixes differ and are not fully disclosed.
- Vintage midpoints revise after every call and Street catch-updirectionally the concentration ladder has been stable even when point estimates move $5–15B per name on a late-Aug step.
- The mid-Q3 desk stack (~$835B) and this late-Aug 202608 stack (~$858B) are related but not identical vintagesdo not splice top-1 shares across those posts without noting the perimeter.
- Figures are USD billions; roundings apply. Do not mix GS GI all-in totals with company share percentages in the same sentence.
Bottom line
The AI capex system remains a concentration system on the late-Aug 202608 tape. On the Big-5 stack of ~$858B, top-1 holds 28%, top-3 holds 74%, and HHI sits near 2,227. The Q3→202608 raise path is even more skewed than the stock: Amazon and Alphabet captured about four-fifths of positive dollar raises while Microsoft and Oracle stayed flat on headline prints. Absolute dollars answered how large the cycle is. Shares answer who is writing it — and for now, that answer remains a short list.