Featured analysis
h5i-db: Point-in-Time Data for Backtests
Point-in-time data stops backtest look-ahead bias at the storage layer. How h5i-db versions every write, and what filing lag data says about stale history.
Market-data research
Strasmore Research
Educational explainers, recurring market-structure breakdowns, and historical deep-dives. Every number is sourced from a stored query against real market data.
Every figure is computed from real US stocks and options market data and stored with the post, so the prose cannot drift from the data.
471 data-backed analyses · 235 evergreen explainers · Updated
- How Options Are Quoted in Volatility Institutions trade options quoted in volatility rather than in dollars. See what a vol quote looks like and how it turns into a cash price at execution.
- When Equal Weight Beats Optimization Equal weight beats optimized position sizing when your sample is short. A seeded Python simulation shows the crossover appear, then close as the sample grows.
- Calendar vs Diagonal Spreads: What Changes Calendar vs diagonal spreads: same short call, one different long strike. See what moving that long strike does to net delta and to the payoff shape.
- How Delta Hedging Actually Works How delta hedging works in practice: the shares a short option book is forced to buy and sell at each close, and why round trips cost the hedger money.
Learn / market data & trading concepts
All 235Evergreen explainers of how US markets actually work, each concept taught with real, queryable market data.
- What Is an Ex-Dividend Date? How It Works The ex-dividend date decides who gets paid: buy before it and the dividend is yours, buy on it and it isn't. See the four key dates on real US timelines.
- The Option Greeks Explained: Delta to Rho Delta, gamma, theta, vega and rho, the five option greeks, demonstrated by tracing one real SPY call through its whole life against the stock.
- What Is VWAP? Volume-Weighted Average Price VWAP stands for volume-weighted average price. Definition: price times volume divided by total volume, reset daily. What it means on a real trading day.
- What Is a Bid-Ask Spread? Real Costs Learn what a bid-ask spread is, how to calculate it, and what it costs per trade, with real spreads measured from tick-level quote data on US stocks.
- What Is RVOL (Relative Volume)? How to Read It RVOL (relative volume) is a stock's volume ÷ its 20-day average: above 1 is busier-than-usual trading. Plus intraday time-of-day RVOL and what counts as high.
- What Is the Closing Auction? (Closing Cross) What the closing auction is, why one 4 p.m. print sets the official close, and how market-on-close orders feed the day's biggest trade, on real tape data.
- How Do Market Makers Make Money? The Spread What market makers do and how they earn the bid-ask spread, with real tick data: measured spreads, quote updates per second, and the SQL behind every number.
- Short Interest vs Short Volume: The Difference Short interest and daily short volume measure different things. See real per-ticker numbers, days-to-cover math, and the exact query behind every figure.
- What Is the 2s10s Spread? Yield Curve Data What the 2s10s spread is, how the Treasury yield curve works, and what past inversions looked like, with every chart built from auditable market data.
- Stock Market Holidays 2026–2027: NYSE & Nasdaq When is the stock market closed? Every upcoming NYSE & Nasdaq holiday and 1:00 p.m. early close for 2026–2027, from the live exchange calendar.
More guides
- Dividend Yield vs Payout Ratio: Key Differences
- Covered Call Closed-End Funds vs ETFs
- Bracket Orders and OCO Orders Explained
- Where to Get Historical Implied Volatility Data
- Broker Exercise Cut-Off Times Explained
- How to Become a Registered Market Maker
- Low P/E Stocks Near 52-Week Lows
- What Does XD Mean on a Stock Quote?
- Stock Splits vs Fractional Shares Explained
- Monthly Dividend ETFs: Who Actually Pays
- Rule 144 and Selling Restricted Stock
- Quadruple Witching vs Triple Witching
- Mutual Fund Frequent Trading Limits Explained
- Event Contract Collateral and Max Loss
- Why ETFs Split and Reverse Split
- Equity vs Index Put/Call Ratio: What's High?
- Why Crypto Has No NBBO: No SIP, No Tape
- Risk-free rate in the Sharpe ratio
- How Annual Dividend Per Share Is Calculated
- Why stocks drop on the ex-dividend date
- Trading Options Inside an IRA: How It Works
- Street Name vs Holder of Record: Cede & Co
- Dividend Yield vs APY: What's the Difference?
- Self-Hosted A-Share Quant Workbench, Explained
- Brier Score: How to Grade a Forecast
- Implied Volatility vs Vega: The Difference
- Ratio Spreads: Breakevens and Naked Risk
- Do Most Options Expire Worthless?
- Cash Settled vs Physical Delivery Options
- Who Sets the Ex-Dividend Date? Not the Board
- What Time Do Mutual Fund Prices Update?
- Warrants vs Call Options: Key Differences
- QuantLib in Rust: libitofin, a Pre-1.0 Port
- Hard-to-Borrow Lists and Borrow Fees
- Held vs Not-Held Orders: Broker Discretion
- How Buffer ETFs Work: Caps and Resets
- How Fractional Shares Hit the Tape
- Mini Index Options Explained: XSP, XND, MRUT
- How ADRs Work: Ratios, Fees and Dividends
- Historical Volatility vs Implied Volatility
- Good Faith Violations in Cash Accounts
- Who Are the Biggest Market Makers?
- Quote-Driven vs Order-Driven Markets
- Dividend Reinvestment Plans (DRIPs) Explained
- How Preferred Stock Dividends Work
- Non-Marginable Securities: Reg T vs House
- MOC and MOO Order Cutoff Times: NYSE & Nasdaq
- Event Contract Arbitrage: YES + NO vs $1
- ETN vs ETF: the credit risk you own
- Early Lockup Release: Triggers and Waivers
- Due Bills and Stock Splits: Ex-Date Timing
- International Fund NAV: Fair Value Pricing
- How Futures Margin Works: SPAN and Calls
- The Vendor Display Rule: SEC Rule 603(c)
- When Is SQ Day for Nikkei 225 Options?
- What Real-Time Market Data Actually Costs
- Schedule 13D vs 13G: Rules and Deadlines
- Market Cap and Which Share Count It Uses
- Cost Basis Methods: FIFO vs Specific ID
- How Event Contracts Settle: Payout and Fees
- Midpoint Peg Orders Explained: Half-Cent Fills
- How to Read a Futures Symbol (ESZ6, CLF27)
- Pin Risk at Options Expiration Explained
- What Is Form N-PORT? Fund Holdings Filing
- Qualified Dividend Holding Period: 61 Days
- Fully Paid Securities Lending Explained
- When Did the US Stock Market Start? 1792
- Stop Order vs Stop-Limit Order: How Each Fills
- How to Read a Form 4 Insider Trading Filing
- Professional vs Non-Professional Market Data
- Dividends vs Buybacks: Shareholder Yield
- Straddle vs Strangle: Break-Evens and Margin
- SEC 30-Day Yield vs Distribution Yield
- Portfolio Dividend Yield: Weighted Average
- Poor Man's Covered Call: How the Trade Works
- Can You Sell on the Ex-Dividend Date?
- Best Time of Day to Sell a Mutual Fund
- Time in Force Explained: Day, GTC, IOC, FOK
- How ETF Creation and Redemption Works
- What Is Option Rho? The Interest Rate Greek
- Iron Condor vs Iron Butterfly: Break-Evens
- Credit Spread vs Debit Spread: Same Trade?
- How to Roll an Option Position: Up and Out
- Level 1 vs Level 2 vs Level 3 Market Data
- Anchored VWAP Explained: Formula and Uses
- Why Your Options Order Isn't Getting Filled
- The Sub-Penny Rule and Price Improvement
- Is a Dividend Safe? Free Cash Flow Test
- Japanese IPO Lockups: The 1.5x Release Rule
- Why Stocks Halt: Limit Up-Limit Down Bands
- What Is a Calendar Spread in Options?
- SpaceX Lockup Expiration Date: How to Find It
- Return of Capital in ETF Distributions
- Payment in Lieu of Dividends, Explained
- Options Expiration Calendar 2026: All 12 Dates
- Margin for Selling Naked Options: Reg T Math
- IV Rank vs IV Percentile: Formulas Explained
- How to Read an Options Symbol (OSI Format)
- How Stock Settlement Works Under T+1
- FINRA Margin Debt Statistics, Explained
- When Are 13F Filings Due? 2026 Deadlines
- What H1 and H2 Mean in Company Reporting
- Why Stock Quotes Are Delayed 15 Minutes
- How the Put/Call Ratio Is Calculated
- Portfolio Delta and Beta Weighting Explained
- $10,000 in a Mutual Fund for 5 Years: The Math
- How Mutual Fund NAV Is Calculated: Example
- Iceberg Orders Explained: Hidden Liquidity
- ETF Premium and Discount to NAV, Explained
- What Is the Sharpe Ratio? Formula and Math
- What Time Do Options Stop Trading?
- Stock Dividend vs Cash Dividend, Explained
- How to Calculate Covered Call Returns
- Put-Call Parity Explained, With Real Numbers
- When Does a Stock Split Take Effect?
- REIT Payout Ratio: FFO vs EPS Explained
- Dividend Withholding Tax for Non-US Investors
- What Is Maximum Drawdown? Depth vs Recovery
- How Implied Volatility Is Calculated
- What Is the High-Low Index? Market Breadth
- When Is the COT Report Released?
- US Market Hours and Daylight Saving Time
- How Stock Splits Affect Your Options
- What Happens If an Option Expires In the Money
- How to Find a Stock's Earnings Date
- Price Return vs Total Return: The Real Gap
- Can an AI Trading Track Record Be Verified?
- Circuit Breakers for Trading Bots
- When Do Mutual Funds Pay Dividends?
- Event Contract Prices as Probabilities
- How to Find a Lockup Expiration Date
- Nikkei 225 Options and SQ Settlement
- DAX Daily Options: How Eurex 0DTE Works
- Highest Dividend Yield US Stocks in 2026
- Trailing vs Forward Dividend Yield Explained
- Learn Quant Trading From an Open Source Book
- Mutual Funds vs ETFs: What Actually Differs
- S&P 500 Dividend Yield: How It's Measured
- SCHD vs VOO: Why the Dividend Yields Differ
- How to Calculate Dividend Yield: 3 Ways
- Pattern Day Trader Rule: What Replaced It
- How Risky Is Options Trading? The Mechanics
- Can You Trade US Stocks 24 Hours a Day?
- Selling Mutual Funds at a Loss: How Basis Works
- When Do Mutual Fund Trades Settle?
- The 3-5-7 Rule in Options, Examined
- What Is a Good Dividend Yield in 2026?
- Paper Trading Before Real Money
- Dividend Payout Ratio: How to Calculate It
- What $1,000 a Month in Dividends Takes
- What Is the VIX? What It Really Measures
- What Is Max Pain in Options? The Real Math
- Trading US 0DTE Options From Japan
- Monthly Dividend Stocks Explained
- Is High Implied Volatility Good? IV in Context
- How to Read an Option Chain, Column by Column
- The 8-4-3 Rule for Mutual Funds, Explained
- 0DTE Options Strategies: How They Trade
- What Is the Efficient Market Hypothesis?
- Covered Call vs Cash-Secured Put
- US Stock Market Hours Around the World
- Covered Call vs Collar: Income or a Floor
- The Wheel Strategy: How the Loop Works
- American vs European Options Explained
- Free Stock Market Data API, No Key Required
- Free SQL API for Stock Market Data
- What Is Volatility Skew? The Smile, Measured
- What Is IV Crush? Measured on Real Earnings
- Which Stocks Have Daily Options?
- When Is Short Interest Released?
- The Low-Volatility Anomaly
- How Often Do Stocks Split?
- Highest Days to Cover Stocks Right Now
- Triple Witching 2026 Dates and Volume Data
- How Ex-Dividend Dates Affect Options
- Does a Stock Go Up After a Split?
- What Is a Special Dividend? (With Examples)
- How Leveraged ETFs Work (and Why They Decay)
- What Is Option Vega? Volatility Sensitivity
- What Is Implied Volatility? IV, Explained
- What Is Option Theta? Time Decay Explained
- What Is Option Gamma? Delta's Accelerator
- What Is Option Delta? A Plain-English Guide
- Most Shorted Stocks Right Now, Measured
- Unusual Volume Stocks This Week, Measured
- Is the Stock Market Open Today?
- When Do 0DTE Options Trade? By the Hour
- When Do Mutual Funds Trade? NAV Pricing at 4 pm
- What Is Average Daily Volume (ADV)?
- IPO Lockup Expiration: Meaning & Release Date
- FINRA Short Interest Data, Explained
- Upcoming Ex-Dividend Dates: Stocks This Week
- What Is Dividend Yield? What's Normal in 2026
- What Is a Short Squeeze? GameStop, Measured
- What Is the Put-Call Ratio? A Data Guide
- DTE Meaning in Options: Days to Expiration
- What Is Triple Witching? Volume & Volatility
- When Do Options Expire? Friday 4 PM ET & Daily
- Why Do Stocks Gap Up or Down Overnight?
- What Is Days to Cover? Short Interest Ratio
- What Is a Stock Split? Ratios and Mechanics
- Market Order vs Limit Order, Measured
- How Monthly Stock Returns Are Measured
- How Much Does It Cost to Trade Options?
- How Big Is the OPRA Options Quote Feed?
- What It Costs to Trade a Stock, Measured
- What Is the NBBO? National Best Bid and Offer
- What Is FINRA Short Interest? Days to Cover
- What Is a Reverse Stock Split? Good or Bad?
- Stock Market Hours: Open 9:30, Close 4:00 ET
- Ex-Dividend Date vs. Record Date: Same Day?
- Locked and Crossed Markets, Explained With Data
- Options Volume vs. Open Interest, Explained
- What Is 0DTE? Zero Days to Expiry Options
- Why Are Spreads Wider at the Open? Real Data
- What Is the Opening Auction? How Stocks Open
- What Is Dark Pool Trading? FINRA Volume Data
- Stock Float vs. Shares Outstanding Explained
- What Is a Block Trade? Big Prints & the Data
- The Most Common SEC Filings, Explained by Data
- Premarket and After-Hours Trading Hours (ET)
- Why Short Interest Data Is Always Two Weeks Old
Deep Dives / forensic investigations
All 111Forensic, single-subject investigations into individual stocks, events, and market-structure quirks.
- Trade Markouts Explained: Execution Quality What is a trade markout? The sign convention explained in plain English, plus a real markout curve measured at horizons from 1 second out to 5 minutes.
- NYSE Parity and D-Quotes: How Fills Allocate NYSE parity splits a fill across participants at the same price, so a floor broker can trade ahead of an earlier public order. See the allocation math.
- How Option Closing Marks Are Set An option closing mark is not the last sale, the bid or the midpoint. See how end of day marks are set, why they move on almost no volume, and what that breaks.
Market Recaps / period-by-period reviews
All 125What actually happened, period by period: daily, weekly, monthly, and beyond, in the numbers.
- Market Recap: July 30, 2026, The Day in Numbers July 30, 2026, measured from the tape: index scoreboard, breadth, sector spread, options flow, the quote tape, rates and calendar, every figure query-backed.
- Market Recap: July 28, 2026, The Day in Numbers July 28, 2026, measured from the tape: index scoreboard, breadth, sector spread, options flow, the quote tape, rates and calendar, every figure query-backed.
- Market Recap: July 27, 2026, The Day in Numbers July 27, 2026, measured from the tape: scoreboard, breadth, sector spread, options flow, the quote tape, rates and the calendar, every figure query-backed.