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ex-Citadel portfolio manager, just explained why almost every fund actually blows up. "90% of hedge fund failures, PM failures, analyst failures, it's bad portfolio construction, sizing, all those things." the logic: alpha is competitive. one good idea barely moves the needle, because the moment you build a book, correlation...

39,360 views • 1 month ago •via X (Twitter)

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Ex-Citadel PM Rich Falk-Wallace (Rich Falk-Wallace) on why 90% of hedge fund blowups are portfolio construction — not bad ideas. Rich Falk-Wallace (PM @ Citadel | Viking Global | Silver Point | Now founder & CEO of Arcana Arcana — risk & portfolio software used by ~7 of the 10 largest multi-manager hedge funds) "When they blow up, the story is never 'Shucks, I actually am not as brilliant as I was before.' What they got wrong was risk, portfolio construction." We cover: - Why 90% of PM failures come from sizing & portfolio construction, not thesis quality - The only two ways to survive long-term: extreme hit rate/slugging, or managing ex-ante correlation - The math of 10 pods long the same trade: factor bets compound, idio bets diversify - Why LTCM is the classic backward-looking correlation failure — and why ex-ante is the whole job - The paradox: "pure fundamental" concentrated funds take the biggest factor bets (up to 80% R²) - Why the best PMs treat every factor exposure like a stock position — same limits, same diligence - Sharpe ratio as a t-statistic against the null hypothesis that you have no skill - The tiger cub who moved to a pod seat and said it felt like playing a video game - Are junior analysts screwed? Dispersion, not extinction - His contrarian take: capital is opening up beyond the Big Four via SMAs Highlights: (00:00) Intro (01:10) The real job of a hedge fund PM: a product sold to allocators (02:52) The 90% failure vector: risk leakage, not bad theses (10:25) Two ways out: hit rate/slugging vs. managing correlations (18:17) Factor bets compound, idio diversifies: why 80% idio becomes 60% at scale (27:33) Factor models as the "perfect benchmark" for every stock at every moment (38:57) The old-school PM who calls factors bullshit — Rich's answer (44:48) Treat factors like stock positions: limits, diligence, sizing (55:29) Why concentrated "pure fundamental" books take the biggest factor bets (01:05:34) Are junior analysts screwed? AI, mock books, & dispersion (01:15:52) Contrarian take: SMA capital opening up beyond the Big Four (01:19:42) The #1 new-launch killer: trying to do too many things at once

Ethan Kho

518,894 views • 1 month ago

Harry Markowitz, the Nobel laureate who invented modern portfolio theory: "Every fund from Bridgewater to Citadel runs on one equation I wrote as a 25-year-old grad student. Wall Street pays quants $500K to use it. It's free." the thread above teaches you to build a portfolio the real way, with the mathematics of capital allocation. every line of it traces back to one paper markowitz wrote in 1952. before him, "don't put all your eggs in one basket" was folklore. he turned it into algebra. he proved a portfolio's risk isn't the average of its parts, it's driven by how the parts move together, the covariance. combine assets that don't move in lockstep and you cut risk without giving up return. that is the closest thing to a free lunch in all of finance, and he wrote the exact equation for how much of it you get. that single insight, mean-variance optimization, is the engine under every serious fund on earth. renaissance, bridgewater, citadel, your pension, all of them size risk with markowitz's math. he published it in 1952, won the nobel in 1990, and it sits in every textbook and this free lecture. same story i keep telling: the math that runs the trillion-dollar machine has been public and free for seventy years. here is the part markowitz himself warned about. the equation is only as good as the numbers you feed it, your estimates of return and covariance. feed it garbage and the "optimal" portfolio it hands back is confidently, precisely wrong, and it detonates in the exact crisis it was built to survive. the optimizer is free. estimating the future honestly, and knowing when to distrust your own inputs, is the entire job.

Rossst.03

44,131 views • 27 days ago

One common reason why traders blow up is because of poor position sizing. In other words, how much do you bet on a trade. You can be right on direction 60% of the time and still lose everything if you size your positions poorly. One oversized trade can wipe out months of gains. This is why position sizing is a big part of risk management. Sandeep Rao - SEBI Reg. RA🖖 recently spoke to Tom Basso, one of the original Market Wizards, to discuss his approach to trading. I was listening to the interview and the one thing that stood out to me was how Tom's thinking on position sizing evolved over decades. He started simple: risk the same percentage of equity on every trade, inspired by Larry Hite's philosophy that every bet should be equal in terms of potential loss. But then came a silver trade with explosive volatility. Clients were calling, nervous about the wild swings. So he realized it wasn't just about the amount you could lose—it was also about the speed of movement. High volatility creates psychological stress that leads to poor decisions. So he added a second layer: volatility as a percentage of equity. Now he'd calculate both risk % and volatility %, then take the smaller of the two. Then came the third refinement: margin-to-equity ratios. Some markets have deceptively low risk and volatility but require high margin because of sudden jump risk. By incorporating all three factors, he never got caught overexposed. The result was a position sizing system that automatically scales down when markets get too volatile, protects against margin squeezes, and keeps portfolio risk in check. It's really interesting conversation. Link to the full interview is in the comments.

Nithin Kamath

59,268 views • 7 months ago