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Code examples, market analysis, and data quality deep-dives.

How to Get Historical Market Cap Data in Python
How Much of the S&P 500 Survives 20 Years? Index Turnover Analysis in Python
Does Joining the S&P 500 Bring New Institutional Owners? 13F Event Study in Python
Is Volatility Seasonal? Calendar Month Analysis of Realized Volatility in Python
Does Fast Revenue Growth Force Companies to Borrow? Cash Funding Analysis in Python
How Far Back Does SEC EDGAR Data Go?
Are One-Time Charges Really One-Time? Charge Frequency Analysis in Python
Does Buying the Dip Work? Short-Term Reversal by Volatility Regime in Python
Alpha Vantage vs Massive vs xfinlink for Fundamentals
How Long Does a Stock Take to Recover From a 50% Fall? Drawdown Analysis in Python
Do Companies That Shrink Their Share Count Outperform? Net Buyback Yield in Python
How Much Does the Dow's Price Weighting Distort It? Index Weighting Analysis in Python
How to Get SEC Form 4 Insider Trading Data in Python
Can Anything Predict Next Month's Stock Returns? Out-of-Sample R-Squared Testing in Python
How Much of a Stock's Return Comes From Its Sector? Variance Decomposition in Python
Altman Z-Score: Where To Get It in Python
Do Value Screens Agree on Which Stocks Are Cheap? Multiple Overlap Analysis in Python
Annual vs Quarterly Financial Data: Which to Use
Do High Returns on Capital Persist? ROIC Fade Analysis in Python
Does Past Beta Predict Future Beta? Beta Stability Testing in Python
Do Defensive Sectors Actually Defend? Up and Down Capture in Python
How to Choose a Financial Data API
Do Small Caps Actually Beat Large Caps? Size Premium Test in Python
What If You Miss the Market's Best Days? Extreme-Day Analysis in Python
Does Rebalancing Add Return? Fixed-Weight vs Drift Portfolios in Python
Which S&P 500 Companies Are Closest to Default? Merton Distance-to-Default in Python
What Happens to Stocks Removed From the S&P 500? Replacement Pair Analysis in Python
Does the Golden Cross Work? 50/200 Moving Average Crossover Backtest in Python
Financial Data for Academic Finance Research
Does Skipping the Most Recent Month Improve Momentum? S&P 500 Decile Sorts in Python
Does Cointegration Survive Out of Sample? Pairs Trading Validation in Python
Which Dividends Are Not Covered by Cash? Free-Cash-Flow Coverage Screening in Python
GICS vs SIC vs NAICS: Which Industry Classification to Use
How Many Stocks Does It Take to Diversify? Random Portfolio Simulation in Python
How Many Days of Data Does a Volatility Estimate Need? Range-Based Estimators in Python
How Much of S&P 500 Cash Flow Is Stock Compensation? Cross-Sectional Analysis in Python
What Is a 13F Filing? Institutional Holdings Explained
Does Revenue Growth Explain Profit Growth? Cross-Sectional Decomposition in Python
How Much of the Nasdaq 100 Is Already in the S&P 500? Index Overlap Analysis in Python
How Often Does a 99% Value-at-Risk Limit Actually Break? VaR Backtesting in Python
Real-Time vs End-of-Day Market Data: Which Do You Need?
How Concentrated Are S&P 500 Earnings? Point-in-Time Index Analysis in Python
Does Volatility Scale With the Square Root of Time? Variance Ratio Test in Python
Does Goodwill Distort the Price-to-Book Screen? Goodwill-Adjusted Valuation in Python
How Are Shares Outstanding Reported (and Why They Disagree)
Do Low-Volatility Stocks Deliver Better Risk-Adjusted Returns? S&P 500 Quintile Sorts in Python
Does Trend Following Beat Buy and Hold? Time-Series Momentum in Python
Has the Stock-Bond Correlation Flipped? 60/40 Portfolio Risk in Python
What API to Use for a Stock Screener
Which Assets Hedge Inflation Shocks? Macro Factor Betas in Python
Does Covariance Shrinkage Beat the Sample Covariance? Minimum-Variance Portfolios in Python
Do Faster Inventory Turns Mean Thinner Margins? Gross Margin Return on Inventory in Python
SEC EDGAR API vs Fundamentals API: Which to Use
Does Fast Earnings Growth Persist? Rank Correlation Analysis in Python
Split Adjustment Explained: Adjusted Close vs Close
Which Trading Day of the Month Pays Best? Turn-of-the-Month Analysis in Python
Can You Use Yahoo Finance Data Commercially?
How Many Independent Bets Does a Nine-Sector Portfolio Give You? Eigenvalue Analysis in Python
Which Volatility Forecast Wins One Month Ahead? HAR vs EWMA in Python
How Concentrated Are Institutional Equity Portfolios? Form 13F Concentration Analysis in Python
Do Stocks Earn Their Returns Overnight or Intraday? Return Decomposition in Python
When Do Corporate Insiders Actually Trade? Form 4 Timing Analysis in Python
Data Requirements for Backtesting a Trading Strategy
What Is Survivorship Bias in Backtesting?
Do High Dividend Yields Come From Bigger Payouts or Falling Prices? Yield Decomposition in Python
Do Stocks Fall Harder Than They Rise? Downside Beta vs Upside Beta in Python
Does Volatility Targeting Improve Sharpe Ratios? Seven-Asset Backtest in Python
Free Stock Market Data APIs: What You Actually Get
How to Give an LLM Financial Data With an MCP Server
Does Post-Earnings Announcement Drift Survive Real Filing Dates? PEAD Event Study in Python
Do Insider Buying Clusters Predict Returns? Signal Testing in Python
Does the S&P 500 Index Effect Still Exist? Event Study in Python
Are Companies Leaving the S&P 500 Faster Than They Used To? Index Survival Analysis in Python
Does Gross Profitability Predict Stock Returns? Quintile Factor Test in Python
What Growth Rate Is the Market Pricing In? Reverse DCF in Python
Does a Strong Balance Sheet Cushion Drawdowns? Leverage and Downside Risk in Python
Does Ticker Recycling Corrupt a Mean-Reversion Backtest? Entity-Resolved Z-Scores in Python
How Much of a Growth Screen's Backtested Edge Is Survivorship Bias? Point-in-Time Index Testing in Python
Why Do Leveraged ETFs Decay? Measuring Volatility Drag in Python
Are Consumer Staples Margins Shrinking Under Inflation? Gross Margin Trend Analysis in Python
Do Weak Jobs Reports Predict Market Drawdowns? NFP Surprise Event Study in Python
Is the Rotation From Tech to Industrials Backed by Earnings? Relative EPS Growth Analysis in Python
Is the Semiconductor Rally Broadening Beyond NVIDIA? Return Dispersion Analysis in Python
Which Stocks Benefit Most When Oil Prices Fall? Oil Beta Screening in Python
Do Bond Returns Predict Stock Returns? Granger Causality Test in Python
Which Stocks Actually Drive Portfolio Returns? Shapley Value Attribution in Python
Does "Sell in May" Still Work? Calendar Anomaly Backtest in Python
How to Build Complete Price History Through Ticker Changes? Entity Resolution in Python
Are KO and PEP Cointegrated? Pairs Trading Signal Construction in Python
Which Commodities Have the Strongest Momentum? Rotation Backtest in Python
Which Commodity ETFs Have the Worst Tail Risk? Expected Shortfall in Python
Are Gold Miners Leveraged Gold Bets? Rolling Beta Analysis in Python
Does the Base-Metals-to-Gold Ratio Lead Cyclical Stocks? Signal Test in Python
Can Risk Parity Tame Commodity Volatility? Portfolio Optimization in Python
Are Power Stocks Becoming an AI Infrastructure Trade? Momentum Screening in Python
Which AI Chip Stocks Have Margin Momentum? Profitability Trend Analysis in Python
Which AI Stocks Are Cheapest Relative to Growth? Growth-Adjusted Valuation in Python
Does AI Stock Leadership Persist? Momentum Backtest in Python
Which AI Stocks Have the Cleanest Balance Sheets? Net Cash Screening in Python
Can Risk Parity Reduce Mega-Cap Drawdowns? Portfolio Optimization in Python
Which Growth Stocks Are Self-Funding? Cash-Flow Quality Screening in Python
Which Sectors Struggle When the Dollar Rallies? Sector Rotation Analysis in Python
Do Cheap Stocks Hold Up When Bonds Sell Off? Valuation Rotation in Python
Does the Nasdaq 100 Have Better Growth Quality Than the Dow? Index Constituent Analysis in Python
Do Healthcare Cash-Flow Margins Predict Returns? Signal Evaluation in Python
Which Dividend Stocks Survive a Cash-Flow Stress Test? Dividend Screening in Python
Does Heavy Insider Selling Predict Weak Returns? Insider Flow Test in Python
Can Quality Screens Reduce Small-Cap Balance-Sheet Risk? Russell 2000 Test in Python
Which Retailers Have Positive Operating Leverage? Margin Screening in Python
Is MSTR a Leveraged Bitcoin Proxy? Rolling Beta Analysis in Python
Is Micron's Memory Cycle Recovering? Inventory and Margin Forecasting in Python
Which Sectors Work When Bonds Rally? Rate-Sensitive Rotation in Python
Do One-Month Price Extremes Reverse? Signal Evaluation in Python
Do Low-Volatility S&P 500 Stocks Reduce Drawdowns? Factor Test in Python
Is AI Capex Paying Back Fast Enough? Revenue Hurdle Forecasting in Python
Could Shorter AI Asset Lives Hit Earnings? Depreciation Stress Test in Python
How Much AI Capex Risk Can a Portfolio Remove? Constrained Optimization in Python
Is the AI Capex Trade Crowded? Rolling Volatility and Sector Rotation in Python
Did the AI Boom Come From Existing S&P 500 Members? Point-in-Time Momentum Test in Python
Is AI Revenue Circular? Customer-Vendor Capex Loop Analysis in Python
Is the AI Trade Connected to Private Credit? Rolling Correlation Network in Python
Is Apollo More Balance-Sheet Sensitive Than Peers? Leverage Screen in Python
Are AI Earnings Supported by Cash Flow? Accrual and Capex Screen in Python
Can Defensive Stocks Hedge AI Drawdowns? Basket Regime Test in Python
How Fast Does the Market Price In Fed Decisions? FOMC Event Study in Python
How Much Are Options Sellers Overpaid? The Variance Risk Premium in Python
Which Companies Have the Worst Earnings Quality? Sloan Accrual Screen with Geographic Revenue Data in Python
Does the Oil-to-Gold Ratio Signal Recessions? XLE/GLD Backtest in Python
Is AI Spending Crowding Out Free Cash Flow? Capex Sustainability Across the Mag 7 in Python
Does a Long Energy / Short Bonds Portfolio Capture Inflation Surprises? Factor Construction in Python
Can a Hidden Markov Model Detect Oil Market Regimes? HMM Analysis in Python
Do Grain Prices Predict Food Inflation? Granger Causality Test in Python
Does the Corporate Credit Spread Predict Stock Market Crashes? BAA-AAA Spread Analysis in Python
Do Oil Stocks Hedge Inflation? Rolling Beta Analysis in Python
Which Stocks Are Most Rate-Sensitive? Equity Duration via Bond Beta in Python
Which Companies Have the Highest Accrual Ratios? Earnings Quality Screening in Python
Is Alpha Persistent or Decaying? Rolling Sharpe Ratio Analysis in Python
Are Markets Trending or Mean-Reverting? Hurst Exponent Analysis in Python
Is Consumer Discretionary vs Staples a Leading Indicator? XLY/XLP Ratio Analysis in Python
Does Heavy Capex Predict Future Stock Returns? Capital Expenditure Analysis in Python
How to Estimate Cost of Equity Using CAPM in Python
Is Volatility Predictable? Testing for Volatility Clustering in Python
Which Industrials Are Overleveraged? Net Debt to EBITDA Screening in Python
GM Before and After Bankruptcy: Why Entity Resolution Matters for Financial Data
What Is Adjusted Beta? Merrill Lynch Beta Shrinkage in Python
How Good Is a Stock Pick? Information Ratio and Tracking Error in Python
Do Stock Returns Follow a Normal Distribution? Testing for Fat Tails in Python
Which Large Caps Have the Highest Free Cash Flow Yield? FCF Screening in Python
Which Sectors Won Over 5 Years? Sector Rotation Analysis in Python
How to Forecast Stock Volatility with GARCH Models in Python
Are Stock Prices Mean-Reverting? Augmented Dickey-Fuller Test in Python
How to Calculate CAPM Alpha and Beta with Regression in Python
How to Compare Sector Sharpe Ratios and Sortino Ratios in Python
DELL: Why Stitching Historical Price Data Together Is Wrong
How to Analyze Drawdown and Recovery for Bank Stocks in Python
How to Screen SaaS Stocks by Revenue Growth and Cash Flow in Python
How to Screen REITs by Dividend Yield and Valuation in Python
How Correlated Are the Magnificent 7? Intra-Group Correlation in Python
AAPL vs XOM: Do Individual Stocks Have Seasonal Patterns?
How to Rank Large-Cap Stocks by Momentum in Python
How to Build a Multi-Endpoint Financial Dashboard in Python
How to Compare Volatility Across Energy Stocks in Python
How to Screen Healthcare Stocks by Valuation in Python
How to Build a Sector Correlation Matrix for Portfolio Diversification in Python
How to Find Oversold and Overbought Stocks Using Z-Scores in Python
How to Measure Earnings Quality: Cash Flow vs Net Income in Python
How to Build a Multi-Factor Stock Screen in Python (Value + Momentum + Quality)
How to Build a Simple DCF Model for Any Stock in Python
How to Screen Tech Stocks by Revenue Growth in Python
How to Screen Stocks by Balance Sheet Health in Python
Is "Sell in May" Real? SPY Monthly Seasonality Over 10 Years
How to Compare Sector Performance YTD Using Python
How to Screen Dividend Stocks by Yield and Quality in Python
How to Calculate Max Drawdown and Recovery Time for Any Stock in Python
How to Compare Profitability Across Mega-Cap Tech Stocks in Python
Why Ticker Symbols Are Unreliable: The Recycling Problem Every Quant Should Know
How to Calculate and Compare Stock Volatility in Python
How to Screen Blue-Chip Stocks by P/E Ratio in Python
How to Track Companies Through Ticker Changes, Bankruptcies, and Renames in Python
S&P 500 Turnover: How Much the Index Has Changed Since 2010
How to Calculate Stock Beta and Correlation in Python
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How to Get SEC Form 4 Insider Trading Data in Python

Insider trading data comes from SEC Forms 3, 4 and 5, the ownership reports that officers, directors and large shareholders file under Section 16 of the Securities Exchange Act of 1934. Form 4 is the one that tracks trades, and it must be filed “before the end of the second business day following the day on which a transaction resulting in a change in beneficial ownership has been executed” (sec.gov Form 4, read 10 August 2026). Every filing is public on EDGAR as an XML document. In Python, xfl.insiders("NVDA", period="1y") returns one row per transaction with the SEC transaction code already decoded, and that decoding is what decides whether the analysis holds up.

What are Forms 3, 4 and 5?

Section 16 obliges a director, an officer, or a beneficial owner of more than 10% of a registered class of equity securities to report both holdings and trades. Three forms carry the obligation, and each has its own clock.

Form 3 is the initial statement of what an insider already owns, filed “within 10 days after the event by which the person becomes a reporting person” (sec.gov Form 3, read 10 August 2026). Form 4 reports each subsequent change in beneficial ownership on the two-business-day clock quoted above. Form 5 sweeps up transactions that were exempt from Form 4 or were simply missed, and is filed “on or before the 45th day after the end of the issuer’s fiscal year” (sec.gov Form 5, read 10 August 2026).

That two-day deadline is the reason Form 4 is worth reading at all. Compare it with a Form 13F, the quarterly institutional holdings report explained in the 13F guide: a 13F arrives up to 45 days after the quarter it describes and names funds rather than people. A Form 4 names the person, the trade date, the share count and the price, usually within the week.

Why is the raw EDGAR feed hard to use for analysis?

Access is not the obstacle. Shape is.

Each Form 4 is a separate XML document, and one document can carry several transaction lines split across two tables, one for ordinary shares and one for derivatives. Building a panel means walking the daily filing index, fetching every document, and flattening those tables into rows. The SEC caps automated access at “10 requests/second” and asks callers to declare a User-Agent header carrying a company name and contact address (sec.gov, Accessing EDGAR Data, read 10 August 2026), so the exercise is a rate-limited crawl rather than a download.

A bulk route exists. The SEC publishes Insider Transactions Data Sets extracted from Forms 3, 4 and 5, covering January 2006 to June 2026, and states that “the data sets will be updated quarterly” (sec.gov, read 10 August 2026). That removes the crawl and adds two constraints in its place: history begins in 2006, and the current quarter is absent until the next posting. The same tradeoff appears in fundamentals, and the EDGAR API comparison works through it in more detail.

Either route leaves the harder problem untouched. The filing carries a raw transaction code, a single letter, and nothing that tells a program what the letter means.

How do you pull Form 4 data in Python?

import xfinlink as xfl

xfl.set_api_key("YOUR_API_KEY")  # free at https://xfinlink.com/signup

df = xfl.insiders("NVDA", period="1y")
df["date"] = df["transaction_date"].dt.date

print(df[["date", "insider_name", "insider_role", "transaction_code",
          "transaction_type", "shares", "transaction_price"]].head(5).to_string(index=False))
print(df["transaction_type"].value_counts().to_string())
      date   insider_name insider_role transaction_code transaction_type  shares  transaction_price
2026-08-05     COXE TENCH     Director                G             gift  500000                0.0
2026-06-25  HUDSON DAWN E     Director                A   grant_or_award    1211                0.0
2026-06-25    Dabiri John     Director                A   grant_or_award    1211                0.0
2026-06-25 Neal Stephen C     Director                A   grant_or_award    1211                0.0
2026-06-25   LORA MELISSA     Director                A   grant_or_award    1211                0.0

transaction_type
open_market_sell    361
grant_or_award       24
tax_withholding      23
gift                 15
other                 5

Both the raw transaction_code and a decoded transaction_type sit on every row, alongside the insider name, the role, the acquired-or-disposed flag, the share count, the price, and the holdings figure after the transaction. History runs back to 1996, and form_type separates Forms 3, 4 and 5 when a study needs only one of them. The full field list is in the docs.

Which Form 4 transaction codes matter?

Eight codes account for almost everything a large company files. The SEC descriptions below are quoted from the Form 4 general instructions (sec.gov, read 10 August 2026).

Code SEC description What it means for analysis Decoded value
P “Open market or private purchase of non-derivative or derivative security” The insider paid cash. The signal everyone is looking for. open_market_buy
S “Open market or private sale of non-derivative or derivative security” A genuine sale, though often a scheduled one. open_market_sell
A “Grant, award or other acquisition pursuant to Rule 16b-3(d)” Compensation. No decision to buy is expressed. grant_or_award
F “Payment of exercise price or tax liability by delivering or withholding securities incident to the receipt, exercise or vesting of a security issued in accordance with Rule 16b-3” Shares withheld to settle a tax bill. Mechanical. tax_withholding
M “Exercise or conversion of derivative security exempted pursuant to Rule 16b-3” An option turning into stock, not a purchase. option_exercise
G “Bona fide gift” A transfer at no price. gift
D “Disposition to the issuer of issuer equity securities pursuant to Rule 16b-3(e)” Sold back to the company, not into the market. sale_to_issuer
C “Conversion of derivative security” A change of instrument. conversion_of_derivative

Codes A, F, M and G describe things that happen to an insider rather than things an insider chooses. They dominate the row count.

What is the most common mistake in insider analysis?

Counting every disposition as a sale. The acquisition_or_disposition flag reads “D” for an open-market sale, for shares withheld to pay tax, for a gift, and for the disposal leg of an option exercise, so a filter on that flag alone sweeps all four into one number.

Across eight large caps over three years, the difference is not marginal.

tickers = ["AAPL", "MSFT", "JPM", "XOM", "KO", "WFC", "GM", "PFE"]
d = xfl.insiders(tickers, period="3y")

sold = d[d["acquisition_or_disposition"] == "D"]
print(sold.groupby("transaction_type")["transaction_value"].agg(["size", "sum"])
          .sort_values("sum", ascending=False).to_string())

open_market = sold[sold["transaction_type"] == "open_market_sell"]["transaction_value"].sum()
print(f"every disposition counted as selling: ${sold['transaction_value'].sum()/1e9:,.2f}bn")
print(f"open-market sales only:               ${open_market/1e9:,.2f}bn")
                  size           sum
transaction_type
open_market_sell   388  2.006649e+09
tax_withholding    508  1.419691e+09
other                2  3.120996e+05
gift                72  0.000000e+00
option_exercise     30  0.000000e+00

every disposition counted as selling: $3.43bn
open-market sales only:               $2.01bn

The naive figure is 1.71 times the real one. Tax withholding alone supplies $1.42 billion of the gap, spread over 508 rows, and those shares never reached the market: the issuer withheld them at vest to settle the recipient’s tax liability. A dashboard built on the disposition flag reports a wave of executive selling every time restricted stock vests on schedule.

How do you filter to the transactions that carry signal?

Filter on the decoded type rather than the direction, and add a size floor so that token purchases do not crowd the result.

buys = xfl.insiders(tickers, period="3y",
                    transaction_type="open_market_buy",
                    min_value=250_000)
buys["date"] = buys["transaction_date"].dt.date

print(buys[["ticker", "date", "insider_name", "insider_role",
            "shares", "transaction_price", "transaction_value"]]
      .sort_values("date", ascending=False).to_string(index=False))
ticker       date       insider_name insider_role  shares  transaction_price  transaction_value
   PFE 2026-08-05 Buckley Mortimer J     Director   37632            25.5200       9.603686e+05
   PFE 2026-08-05  BLAYLOCK RONALD E     Director   39231            25.4600       9.988213e+05
    KO 2025-10-24      LEVCHIN MAX R     Director    7206            69.8706       5.034875e+05
    KO 2025-10-23      LEVCHIN MAX R     Director    4197            70.3062       2.950751e+05
  MSFT 2025-04-23 SMITH BRADFORD LEE    President    3842           377.4650       1.450221e+06
   PFE 2025-02-13  BLAYLOCK RONALD E     Director   19457            25.6500       4.990720e+05
    GM 2024-07-26    JACOBSON PAUL A          CFO   25000            44.1100       1.102750e+06
   XOM 2024-06-17    DREYFUS MARIA S     Director   18310           109.2510       2.000386e+06
   XOM 2023-11-06    UBBEN JEFFREY W     Director   50000           105.9882       5.299410e+06
   XOM 2023-11-06    UBBEN JEFFREY W     Director   50000           105.9872       5.299360e+06
   XOM 2023-11-06    UBBEN JEFFREY W     Director  150000           105.9510       1.589265e+07

Eleven rows out of 1,916. That ratio is the point of the whole exercise. Insiders at large companies are paid in stock, so acquisitions arrive on a vesting calendar and disposals arrive on a tax calendar, while a purchase requires the person to write a cheque against a position they already hold. Scarcity is what gives code P its information content, and averaging it together with the other codes destroys exactly that.

The remaining filters narrow it further. insider_role matches a substring, so insider_role="CEO" or insider_role="Director" separates the officers who see the operating numbers daily from board members who see them quarterly. min_value screens on dollars rather than shares, which keeps the comparison honest across a $25 stock and a $380 one. Setting include_amendments=True brings in corrected filings when the audit trail matters.

FAQ

Is Form 4 data free?
The filings are free on EDGAR, and the SEC’s quarterly data sets are free to download. The xfinlink insiders endpoint is on the paid plans; see pricing for the tiers and their limits.

How quickly does a trade appear after it happens?
Form 4 is due before the end of the second business day after the trade, so most transactions become public within a week of execution. Each row carries both transaction_date and filing_date, which is how the reporting lag can be measured directly rather than assumed.

Do open-market purchases predict returns?
That is an empirical question and the answer varies by horizon, company size and role. The requirement is a clean sample first: a study that treats grants and tax withholding as trades is measuring the compensation calendar, not insider conviction.

Built with xfinlink — free financial data API for Python. pip install -U xfinlink

Built with xfinlink — free financial data API for Python. pip install -U xfinlink
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