Quant Mashup - Tradevo Data

Lookahead Bias in Fundamental Backtests: 66 Days, Measured [Tradevo Data]

If your backtest joins fundamentals on the fiscal-period-end date, it is trading on numbers that did not exist yet. That's the whole bug, in one sentence. A company's fiscal year ends, and then — weeks later — a 10-K gets filed and the numbers become public. Join on the wrong date and(...)