ARCH CAPITAL GROUP LTD. (ACGL) Institutional Ownership

Financials · Fire, Marine & Casualty Insurance

Institutional ownership and 13F holdings context for ARCH CAPITAL GROUP LTD. (ACGL) on InvestAtlant.

Top institutional holders (2026-Q3)

Institution	Shares	Value	% Outstanding
GEODE CAPITAL MANAGEMENT, LLC	10,351,923	$952.73M	—
High Ground Investment Management LLP	2,743,417	$253.38M	—
COOKE & BIELER LP	1,831,651	69.17M	—
Bank of New York Mellon Corp	1,505,451	39.04M	—
Sumitomo Mitsui Trust Group, Inc.	853,270	$78.81M	—
WEDBUSH SECURITIES INC	740,334	$387	—
GENERAL AMERICAN INVESTORS CO INC	530,200	$48.97M	—
Russell Investments Group, Ltd.	341,958	$31.82M	—

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Email	Name	Role	Plan	Status

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Getting Started

What is InvestAtlant?

InvestAtlant surfaces publicly disclosed trades and the research behind them, helping you see what institutions and insiders are buying or selling, which securities they are moving into, and when. The platform also tracks publicly disclosed stock trades by members of Congress, including transactions reported through Periodic Transaction Reports (PTRs) under the STOCK Act — alongside stock charts, fundamentals, and SEC filings in one workspace.

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Data & Research

Where does InvestAtlant get its data?

InvestAtlant is built primarily on publicly available disclosures — including SEC filings such as institutional Form 13F holdings, Form 4 insider transactions, company fundamentals from 10-K / 10-Q (and related XBRL), and publicly reported congressional / political trading disclosures — plus market price data used for charts and context. For a fuller list, see Data Sources.

How often is the data updated?

Update cadence depends on the source. Market prices refresh more frequently during trading hours. Insider (Form 4) and political disclosures are ingested on a recurring schedule as new filings appear. Institutional 13F data follows the SEC reporting calendar and is updated as new quarterly filings are published and processed. Exact pipelines and timing are described on Methodology.

What are institutional transactions?

On InvestAtlant, “institutional” activity usually refers to holdings and changes reported by large investment managers in SEC Form 13F filings — for example new positions, increased or reduced stakes, or exits between reporting periods. These are delayed public disclosures of portfolio holdings, not real-time trade tickets.

What are insider transactions?

Insider transactions are trades and related filings by company officers, directors, and certain beneficial owners, typically reported on SEC Form 4. InvestAtlant surfaces publicly disclosed trades and the research behind them, helping you see what insiders are buying or selling, which securities they are moving into, and when.

What is political activity?

The platform tracks publicly disclosed stock trades by members of Congress, including transactions reported through Periodic Transaction Reports (PTRs) under the STOCK Act. These are delayed public filings, not live brokerage feeds.

How do you calculate changes in holdings?

Holding changes are derived by comparing reported positions across filing periods (for example share counts or estimated values between consecutive 13F quarters). Labels such as new, increased, reduced, or sold are based on those period-to-period comparisons. Step-by-step rules live on Methodology.

Why might InvestAtlant's data differ from another website?

Sites may use different filing cutoffs, ticker mappings, share-class handling, amendment timing, currency/unit conventions, or inclusion rules for certain instruments. InvestAtlant focuses on publicly disclosed filings and its own normalization rules — so totals or “change” labels can differ even when both sources are legitimate.

What happens when a filing is amended or corrected?

When an amended or corrected filing is ingested, InvestAtlant updates the relevant records to reflect the latest disclosed information. Historical views may change after amendments land. Processing details are covered in Methodology.

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Overview Data Sources Institutional Holdings Insider Transactions Political Activity Normalization Change Calculations Filing vs Transaction Dates Amendments Limitations Updates What We Don't Do

1. Overview

InvestAtlant aggregates and organizes publicly available financial and government disclosures to make institutional, insider, and political activity easier to research — alongside charts, fundamentals, and related SEC context in one workspace.

InvestAtlant does not create the underlying disclosures. We process, normalize, and present information from public sources so filings can be compared across periods, filers, and tickers.

2. Data Sources

InvestAtlant is built on sources we actually ingest or display. The main categories are:

Institutional activity

SEC Form 13F filings (including 13F-HR and related amendments when ingested)
Institutional investment manager holdings reported in those filings
Related SEC submissions metadata used to discover and process filings

Insider activity

SEC Form 4 transaction filings (primary source for insider buys, sells, and other reported codes)
Forms 3 and 5 are part of the broader SEC beneficial-ownership reporting regime; InvestAtlant's transaction research and signal views focus on Form 4 activity

Political activity

Official congressional financial disclosures (for example House PTR PDFs and Senate EFD reports)
Other applicable public government disclosure sources used by our politician ingest pipeline

Fundamentals & market context

Company financials from SEC Company Facts XBRL (for example metrics used in Filings → Fundamentals and related tools)
Market context via TradingView for interactive charts
Reported institutional position values primarily come from Form 13F filings, not from inventing real-time portfolio marks

A user-facing summary of sources also lives on Data Sources.

3. Institutional Holdings

Institutional holdings are derived from publicly filed Form 13F reports. InvestAtlant extracts reported securities, share (or contract) quantities, and reported values, then normalizes them into a consistent format so positions can be compared across reporting periods and managers.

From consecutive reporting periods we classify activity such as:

New positions — a security appears in the later period but not the prior period
Increased / add — shares held rise versus the prior period
Reduced / trim — shares held fall versus the prior period but remain above zero
Sold-out / exited — a prior position is no longer reported in the later period

We also surface fields commonly used in research views:

Shares held — reported position size for the period
Position value — reported filing value, normalized to USD where needed
Quarter-over-quarter changes — share and (when available) value deltas between periods

Sold-out detection depends on having comparable period coverage for a filer. Missing filings are not treated as exits.

4. Insider Transactions

Insider transactions on InvestAtlant come primarily from SEC Form 4 filings. Each row includes transaction codes and acquisition/disposition flags that describe what happened.

Common classifications include:

Purchases — open-market / private purchase (code P)
Sales — open-market / private sale (code S)
Option exercises — for example code M
Grants / awards — for example code A
Other types — gifts, tax withholdings, and other Form 4 codes when present

Not every Form 4 row is a discretionary buy or sell. Awards, option exercises, gifts, and share withholdings can appear in filings without representing an open-market trade. Research views and signals that focus on “buying” or “selling” typically emphasize open-market codes P and S unless a page explicitly includes other transaction types.

5. Political Activity

InvestAtlant uses publicly available financial disclosures to organize reported securities activity associated with members of Congress and other covered political figures.

Where available, we capture and display:

Reported transactions (for example purchase / sale type)
Transaction date and filing / disclosure date
Security identification (name / ticker when provided)
Reported amount ranges
Amendments when a later disclosure replaces or updates earlier information

Political transactions are often reported as dollar ranges, not exact amounts. InvestAtlant preserves the reported range (and derived min/max bounds). Some analytics may use a midpoint estimate for ranking or aggregation — that estimate is derived from the disclosed range and is not an exact trade size from a brokerage confirmation.

6. Normalization

Raw filings are not always clean or consistent across issuers, filers, and disclosure systems. InvestAtlant may normalize fields such as:

Company names and ticker symbols
CUSIPs and other security identifiers
Security types (for example common stock vs options where distinguished)
Transaction types / codes
Dates (transaction, filing, period end)
Monetary values and share quantities (including 13F value unit handling)

Normalization exists to make different filings comparable in tables, charts, and change calculations. It does not change the underlying public disclosure — it maps that disclosure into a consistent research schema.

7. Change Calculations

When sufficient historical information is available, InvestAtlant calculates changes between reported institutional positions to identify increases, decreases, new positions, and exits.

Shares change: Current shares − Previous shares
Shares percentage change: ((Current shares − Previous shares) / Previous shares) × 100
If previous shares are missing or zero, percentage change is not shown.

Event labels such as new, add/trim, or sold-out are based on those period-to-period share comparisons (and presence/absence of a position), not on live trading activity after the filing date.

8. Filing Dates vs. Transaction Dates

These dates are easy to confuse — especially for 13F research:

Transaction date: When the underlying activity occurred (used heavily for Form 4 and political disclosures).
Filing / disclosure date: When the report was submitted or published to the public source.
Reporting period: The period a filing represents (for example a 13F calendar quarter). A 13F can be published well after the quarter ends.

Holdings shown for a quarter reflect what was reported for that period — not necessarily what a manager holds today.

9. Amendments & Corrections

Public filings can be amended or corrected after their initial submission. When an amended filing is available and processed by InvestAtlant, associated records may be updated to reflect the latest available disclosure.

As a result, historical tables, ownership totals, and change labels can change after amendments are ingested. Duplicate or previously seen filings are treated as no-ops where our ingest pipeline detects them.

10. Data Limitations

Transparency matters. Please keep these limitations in mind:

Filings are reported after the underlying activity occurs.
Some disclosures provide estimated or ranged values, not exact amounts.
Public filings can contain errors or incomplete identification.
Data may be delayed by filing calendars, processing time, or source availability.
Security identification (ticker / CUSIP / name) can sometimes be ambiguous.
Historical information can change when filings are amended.
Reported holdings do not necessarily represent current holdings.

11. Updates

InvestAtlant monitors applicable public filings and updates datasets as new disclosures become available and are processed. This is not a real-time brokerage feed.

In practice, scheduled jobs typically:

Refresh politician disclosures and Form 4 insider data on a recurring daily schedule, then warm related research caches
Process institutional 13F filings during filing windows (and via dedicated 13F ingest jobs), then rebuild ownership caches and institutional signal views
Ingest SEC fundamentals for tracked tickers on a recurring fundamentals job

Exact run times depend on deployment configuration. Charts and quote search refresh according to their market-data providers when those integrations are enabled.

12. What InvestAtlant Doesn't Do

InvestAtlant organizes and analyzes publicly available information. The platform does not determine whether a transaction is a good or bad investment, and the presence of an institutional, insider, or political transaction should not be interpreted as a recommendation to buy or sell a security.

For the full legal wording, see our Disclaimer.

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Stocks ranked by net buying from institutional 13F, insider Form 4, and politician filings — not price performance.

Ownership Movers

Biggest quarter-over-quarter institutional ownership % movers from tracked 13F holders.

Holder Overlap

Stocks also owned by the institutional holders of a selected ticker — plus insider and politician buyers.

Holders also own

Rank	Stock	Overlap count	Overlap %	Weighted score	Conviction score

Institutions holding this stock

Institution	Type	Shares	Value	Weight

Insiders who bought

Insider	Title	Date	Value

Politicians who bought

Politician	Chamber	Date	Est. value

Ownership History

Historical ownership rankings from 13F filings — expansion, adoption, early discovery, and decliners.

Fastest ownership growth —

Biggest holder increase —

Biggest institutional declines —

New institutional discoveries —

—

Comparison summary

Institutional activity

Metric	Stock A	Stock B

Insider activity

Metric	Stock A	Stock B

Politician activity

Metric	Stock A	Stock B

Signals

Signal	Stock A	Stock B

Shared ownership

Activity timeline

Date	Stock A	Stock B

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ACGL

ARCH CAPITAL GROUP LTD.

Institutional ownership

Institutional activity

Quarter-over-quarter changes

Biggest buyers

Top 5 by shares added vs prior quarter (existing positions)

Biggest sellers

Top 5 by shares sold vs prior quarter (still held)

Exits

Funds that filed this quarter and fully sold the stock (not merely late filers)

New positions

Funds that opened a brand-new position this quarter

Institutional options

13F call & put positions

Options bias

(calls − puts) ÷ (calls + puts)

Metric	Value
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Weighted bias

(common + 0.7×calls − 0.7×puts) ÷ total

Metric	Value
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Calls & puts by fund

Top 5 by total exposure · per-fund weighted bias (common + 0.7×calls − 0.7×puts) ÷ total

Fund	Contracts	Common	Calls	Puts	Bias

Insider activity

SEC Form 4 transactions

Insider	Role	Code	Call/Put	Signal	Shares	Price	Value	Date
Select a stock to load insider transactions.

Congress activity

Politician	Chamber	Type	Traded	Amount
Select a stock to load congressional trades.

SEC EDGAR filings

data.sec.gov submissions (recent)

Form	Filing date	Description	Accession

10-K filings

Form	Filing date	Report date	Description

8-K Item 2.02 earnings releases

Filing date	Items	Revenue	Net income	EPS (dil.)	Source

Fundamentals

SEC Company Facts · XBRL

Sector

SIC classification from SEC company submissions

—

Income statement

Latest values from 10-K (FY) or 10-Q (Q1–Q3)

—

Balance sheet

—

Cash flow

—

Derived metrics

Margins, free cash flow, and YoY growth

—

Annual periods (10-K)

FY	Period	Period end	Revenue	Op. income	Net income	EPS (dil.)	Assets	Rev YoY

Quarterly periods (10-Q)

FY	Period	Period end	Revenue	Op. income	Net income	EPS (dil.)	Assets	Rev YoY

13F-implied performance rankings

Portfolio returns from reconstructed 13F holdings

#	Institution	Type	Quarter	Return	Consistency	Ann. volatility

Performance

Ranked by change in reported 13F portfolio value

This ranking reflects changes in the reported value of an institution's disclosed 13F portfolio between filing periods. It is not the institution's actual investment return.

Rank	Institution					Latest Filing Date

Most Accumulated Stocks

Shows which stocks institutions have accumulated the most over the selected period.

Positive accumulation only

New Institutional Positions

Stocks that institutions opened as brand-new positions in their most recent 13F filing.

Total new positions —

Institutions reporting —

Unique stocks —

Total reported value —

			Filing quarter		Shares			Previous position

Completely Sold Positions

Stocks fully exited across tracked institutions, ranked by aggregated prior 13F value.

Stocks fully exited —

Institutions reporting exits —

Total exit events —

Total prior value exited —

						Status

Institution Comparison

Compare the latest reported holdings of two institutional investors.

Institution A

Filing quarter: — Filing date: —

Institution B

Filing quarter: — Filing date: —

Select two institutions to compare their latest 13F filings.

Institution A

Total portfolio value —

Holdings —

Largest holding —

Top sector —

Institution B

Total portfolio value —

Holdings —

Largest holding —

Top sector —

Shared holdings —

Unique to A —

Unique to B —

Portfolio similarity —

Weighted similarity —

Institution A — Top 25

Institution B — Top 25

Stock	Ticker	Position value	Portfolio weight	Shares	Filing quarter

Stock	Ticker	Position value	Portfolio weight	Shares	Filing quarter

Browse by Strategy

Institution Directory

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Institutional filer

Holdings

Top positions by reported value

Ticker	Stock

Activity

Quarter-over-quarter changes

Biggest adds

Existing positions with more shares; ranked by value of shares added (at quarter-end price)

Biggest trims

Existing positions with fewer shares (still held); ranked by value of shares reduced

Exits

Positions held last quarter that are fully sold (current shares = 0)

New positions

Positions not held in the prior quarter

All changes

Every position with a quarter-over-quarter share change

Options

13F call & put positions

Options bias

(calls − puts) ÷ (calls + puts)

Metric	Value
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Weighted bias

(common + 0.7×calls − 0.7×puts) ÷ total

Metric	Value
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Calls & puts by stock

Top 5 by total exposure · per-stock weighted bias (common + 0.7×calls − 0.7×puts) ÷ total

Performance

Reported 13F portfolio value changes

This reflects changes in the reported value of the institution's disclosed 13F portfolio between filing periods. It is not the institution's actual investment return.

Quarter	Portfolio value	QoQ $	QoQ %	Holdings	Filing date

Filings

13F filings on record

Quarter	Filing date	Form	Positions	Reported value

Insider clusters

Executive cluster buying — multiple insiders purchasing within a rolling window.

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#	Ticker	Score	Strength	Buyers	CEO	Buy value	Signal
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Conviction Buys

Open-market Form 4 purchases ranked by conviction — size, ownership increase, role, and repeat buying.

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Highest conviction —

Avg conviction score —

High conviction buys —

Capital deployed —

#		Insider	Role					Label
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Repeat Buyers

Insiders who repeatedly buy open-market shares of the same company — streaks, frequency, and capital deployed.

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Active repeat buyers —

Longest purchase streak —

Largest total investment —

Avg repeat score —

#		Insider	Role							Classification
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Most bullish stocks —

Most bearish stocks —

Net insider buying —

Avg sentiment score —

Stock sentiment rankings

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#		Buyers	Sellers				Classification
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First-ever buyers —

Avg years since last buy —

Highest conviction return —

Total capital invested —

First-time & long-gap purchases

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#		Insider	Role		Previous buy			Classification
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Heavy Selling

Stocks with significant open-market Form 4 selling — clusters, executives, and large sales.

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Largest insider sale —

Cluster selling events —

Executive sellers —

Total insider selling —

#				Shares sold				Classification
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Recent insider trades

SEC Form 4 open-market and administrative insider transactions across ingested issuers.

Browse by Strategy

No insider trades in the database yet. Run npm run db:ingest-insider-form4 -- TICKER or bulk ingest to load Form 4 data.

Insider	Stock	Type	Date	Amount

Most Accumulated Stocks

Stocks with the largest net congressional buying over the selected period.

Largest Portfolios

Politicians ranked by net disclosed portfolio flow (purchases minus sales).

Repeat Buyers

Politicians repeatedly purchasing the same stock across congressional disclosures.

Active repeat buyers —

Longest purchase streak —

Largest estimated investment —

Average repeat buyer score —

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First-Time Buyers

First recorded purchases and returning buys after a multi-year gap — raw disclosure data, no scores.

First recorded buyers —

Returning buyers (3+ years) —

Avg years since previous buy —

Total estimated purchases —


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Heavy Selling

Stocks with significant sell disclosures from members of Congress — factual counts and estimated values only, no proprietary scores.

Largest estimated sale —

Stocks with multiple sellers —

Active politician sellers —

Total estimated value sold —


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Politician Sector Exposure

Explore which sectors members of Congress are investing in based on publicly disclosed trades.

Politicians trading this sector

Politician	Trades	Buys	Sells	Net

Most traded stocks

Stock	Trades	Est. value

Largest purchases

Politician	Stock	Amount	Date

Largest sales

Politician	Stock	Amount	Date

Recent disclosures

Politician	Stock	Type	Amount	Date

Politicians

Congressional stock trading disclosures, periodic transaction reports, and position history.

No filings loaded yet. Run npm run politicians:fetch-recent to pull the latest House and Senate PTRs.

Sector Accumulation

Institutional inflow by sector over the latest 13F quarter.

Industry Accumulation

Institutional inflow by industry over the latest 13F quarter.

Sectors

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Top stocks

Select a sector

Rank
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Sectors

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Top exits

Select a sector

Rank
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Highest score —

Bullish (≥65) —

Tickers ranked —

Rankings

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#	Ticker	Score	Institutional	Insider	Congress	Alignment
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Top institutions

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New positions

Select a fund

Ticker	Issuer
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Total Double Signals —

Unique Stocks —

Institutions Involved —

Insider Purchases —

Double signals

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Institutional and insider buying activity within the selected window.

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Institution activity

Institution	Type	Position value	Shares change	Filing date

Insider activity

Insider	Role	Purchase value	Shares	Date

Timeline

Total Triple Signals —

Unique Stocks —

Institutions Involved —

Insider Purchases —

Politicians Buying —

Triple signals

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Institutional, insider, and politician buying activity within the selected window.

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Institution activity

Institution	Type	Position value	Shares change	Filing date

Insider activity

Insider	Role	Purchase value	Shares	Date

Politician activity

Politician	Party	Chamber	Est. purchase	Date

Timeline

Conflicts —

Inst. buying / Insiders selling —

Inst. selling / Insiders buying —

Double conviction —

Conflict signals

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Gems —

Hidden Gem —

Strong Accumulation —

Institutional Discovery —

Hidden gems

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Highest Conviction —

Average Conviction —

High Conviction Stocks —

Exceptional Conviction —

Comparison

Score · median weight · >2% holders · accumulation

Ticker	Conviction	Median weight	>2% holders	Accumulation

Institutional conviction

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Rank
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New Institutional Discoveries —

New Institutional Positions —

Fastest Holder Growth —

Longest Adoption Streak —

Institutional adoption

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Rank
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Financial inputs

Forecast assumptions

FCF growth by year

Scenario assumptions

Bear / Base / Bull cases use constant FCF growth with their own WACC and terminal growth. Not predictions.

Case	FCF growth %	WACC %	Terminal growth %
Bear Case
Base Case
Bull Case

DCF result

DCF implied value

—

per share

Current price: —
DCF implied upside: —
Enterprise value: —
Equity value: —
Terminal value %: —

Valuation bridge

Present value of forecast FCF

Year	FCF	Discount factor	Present value

Scenarios

DCF range —

Reverse DCF

What constant FCF growth is implied by the current price?

Current price: —
Implied FCF growth: —

Sensitivity

Intrinsic value per share — WACC × terminal growth

Financial data sources

WACC Calculator

Estimate weighted average cost of capital using filing-derived debt, tax rate, and market-based equity assumptions.

WACC (Weighted Average Cost of Capital) estimates the average return required by a company's shareholders and lenders. In a DCF, it is used as the discount rate for future cash flows.

No stock selected

Financial inputs

Cost of equity

What is this?

Cost of debt

Higher WACC → lower DCF valuation

Lower WACC → higher DCF valuation

No stock selected

Financial data

Normalized earnings

Historical margins

WACC

%

EPV uses WACC to capitalize normalized earnings. Higher WACC lowers EPV; lower WACC increases EPV.

Scenario assumptions

Bear / Base / Bull vary normalized margin and WACC only — no growth forecasts.

Case	Normalized margin %	WACC %
Bear Case
Base Case
Bull Case

EPV result

EPV per share

—

Enterprise EPV: —
Equity EPV: —
Current price: —
EPV implied upside: —

Valuation bridge

Scenarios

EPV range —

Sensitivity

EPV per share — WACC × normalized margin

Financial data sources

No stock selected

Financial inputs

Target P/E multiple

Scenario multiples

Case	P/E multiple
Bear Case
Base Case
Bull Case

Result

Implied Share Price

—

Current EPS: —
Selected P/E: —
Current Price: —
Implied Upside: —

Valuation bridge

Scenarios

Bear	Base	Bull

Data sources

No stock selected

Financial inputs

Target EV/EBITDA multiple

Scenario multiples

Case	EV/EBITDA
Bear Case
Base Case
Bull Case

Result

Implied Share Price

—

Implied Enterprise Value: —
Implied Equity Value: —
Current Price: —
Implied Upside: —

Net debt —

Valuation bridge

Scenarios

Bear	Base	Bull

Data sources

No stock selected

ARCH CAPITAL GROUP LTD. (ACGL) Institutional Ownership

Top institutional holders (2026-Q3)

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