US stock market analysis covering NASDAQ, NYSE and S&P 500
--- Price is the effect. The halt is the cause. On March 18, 2020, at 9:30:07 AM ET — seven seconds after the New York Stock Exchange opened — circuit breakers triggered for the entire market. For app
On September 21, 1998, the hedge fund Long-Term Capital Management sent a fax to its investors. The fund had lost $2.1 billion in three weeks. Its partners included two Nobel laureates in economics. I
--- When Small Orders Move Big Markets "Print. 100 shares. Exchange: EDGX. Condition: Dark." At 10:47:03.182 AM on a Tuesday, 100 shares of a $47 stock exchanged hands. No headline captured it. No ind
A momentum strategy that returned 23% in historical simulation lost 11% in live trading. The strategy logic was identical. The execution infrastructure was production-grade. The culprit was a data han
--- The Illusion of the Perfect Algorithm In 1988, mathematician Edward Thorp published his definitive paper on card counting. By 1992, his hedge fund Princeton Newport Partners had returned 20% annua
The spread between two stocks looked like a gift from the market gods. In 2019, two semiconductor companies traded with what appeared to be a near-perfect correlation of 0.94 over a rolling 90-day win
--- "Price is the effect. The order book is the cause." That aphorism circulates in quantitative trading circles for good reason. Every tick of price movement traces back to a visible or invisible tra
--- > "At 3:17 AM on a Tuesday, a memory leak in the order execution module caused the Python process to exit silently. By the time the trader checked the dashboard at 7:00 AM, three hours of opportun
--- The Number That Misled a Generation of Quants The number on the screen read 2.34. Your backtest showed a Sharpe ratio of 2.34 — exceptional by any standard. You ran the strategy for three years ac
On March 9, 2020, the New York Stock Exchange triggered market-wide circuit breakers for the first time since 1997. Trading in S&P 500 components halted for 15 minutes. When markets reopened, some sto
--- The Question Every Trader Should Ask Before Signing Up Two trading strategies are on the table. Strategy A returned 28% last year with a maximum drawdown of 20%. Strategy B also returned 28% last
"Volume is the only honest witness." The saying circulates in quant trading desks for good reason. Price can lie. Indicators can lag. But volume — the raw count of shares exchanged — tells you whether
--- Two strategies. Strategy A posts a Sharpe ratio of 2.1 over three years. Strategy B delivers 1.0. A rational allocator, guided by conventional wisdom, should prefer Strategy A. They should not. In
"Price is the effect. The order book is the cause." At 4:01 PM ET on August 5th, a semiconductor company's Q2 earnings crossed the wire. Revenue beat consensus by 12%. The headline number looked like
The number hit the wire at 8:30 AM ET. 287,000 jobs added in January — well above the 180,000 consensus estimate. EURUSD dropped 87 pips in 11 seconds. This is not an anomaly. It is the predictable co
--- The Model That Worked—Until It Didn't A quantitative researcher spent three months building a stock price prediction model. The model used a feature derived from commodity futures data. In-sample
--- "Three. Two. One." In the trading room where I spent my first year as a quant developer, that countdown was never about a rocket launch. It was about the 8:30 AM ET press release that moves curren
--- The 3 AM Realization At 3:17 AM on a Tuesday, alone in a room illuminated by three monitors and the glow of a Jupyter notebook, a trader watched their mean-reversion strategy trigger its 47th cons
--- The Backtest That Lied to You Imagine you built a mean-reversion strategy on a US-listed stock that went through a trading halt in 2019. Your backtest shows a Sharpe ratio of 2.1. You run it live.
--- The closing bell rings at 4:00 PM ET. Most traders close their terminals and head home. Inside a professional quantitative shop, a different clock starts ticking. Between 4:00 PM and 5:30 PM, a we