Vinesh Jha’s Post

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This recent post by Byrne Hobart, CFA at The Diff about backtests is well worth a read. "And that's just what can go wrong with rebalancing in a backtest while assuming transaction costs to be zero. They're not! There are some systematic strategies that end up more or less measuring the implied cost of whatever the strategy is." - true, but I would add that if you find gross, but not net, alpha in a short-term signal, it can still be useful when combined with other short-term signals. Together, a number of individually unprofitable, uncorrelated trading signals can add up to a profitable strategy. I like the way Byrne concludes: "Most of the time, a backtest represents a partly-proven theory paired with a leap of faith." Yup. The "leap of faith" is what quants often call "intuition," even though many of us misuse the word, or even abuse it by applying it to an ex-post explanation of a successful backtest. https://lnkd.in/gZGQNTRP

"Nobody Knows Anything": Backtests are Hard

"Nobody Knows Anything": Backtests are Hard

thediff.co

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