Does the Piotroski F-Score still work?

Questions

Does the Piotroski F-Score strategy still work?

On QuantGPT's test it did not beat the market. The library's Piotroski run, liquid US stocks with an F-Score of 7 or more (of 8 signals) and price-to-book at most 1.5, the 30 cheapest, re-formed monthly, grew 4.9% a year from 1998 to September 2026, gross of costs, against 9.4% for the S&P 500 with dividends, with a Sharpe of 0.35 against 0.66. It trailed both before 2015 (3.5% against 6.2% a year) and after (6.9% against 14.2%). Over this window the criteria beat the benchmark on neither growth nor Sharpe, which QuantGPT labels NO EDGE. Piotroski found the effect in small, thinly traded value stocks from 1976 to 1996; this test holds liquid stocks only, so it measures a different market.

What are the nine Piotroski signals?

Piotroski (2000) scores a cheap stock 0 to 9, one point for each: positive return on assets, positive operating cash flow, rising return on assets, operating cash flow above return on assets, lower leverage, a higher current ratio, no new equity issued, a higher gross margin and a higher asset turnover. A score of 8 or 9 was the buy group and 0 or 1 the avoid or short group. QuantGPT's f_score factor covers 8 of the 9 (0 to 8): the current-ratio signal is not in its data.

Which academic stock market anomalies still hold up out of sample?

QuantGPT keeps no ranking of them. Each of the 55 runnable entries in its strategy library can be run on the same data, and every run splits its statistics at a cut year (2015 unless you pick another), so the years after the cut read on their own. On that test the Piotroski F-Score trailed the S&P 500 with dividends after 2015: 6.9% a year against 14.2%, gross of costs.

Do famous trading strategies still work?

It depends on the strategy and on the test. A published result covers its authors' years and stocks; a rerun on other years and other stocks is a different test. QuantGPT's library documents 175 strategies from research papers, famous investors and their letters, and 55 of them run in one click on decades of US market history, each against a benchmark, year by year. The Piotroski F-Score is one: on liquid US stocks from 1998 to September 2026 it beat the S&P 500 with dividends on neither growth nor Sharpe, which QuantGPT labels NO EDGE.

Where can I backtest the Piotroski F-Score?

On QuantGPT: from the strategy library with one click (RUN IT on the Piotroski F-Score entry opens it in the terminal), or from Claude or ChatGPT connected over MCP, with a question such as: Use QuantGPT to backtest the Piotroski F-Score from 2005 with scores of 7 and up, and show the losing years. You can change the start year, the score cutoff, the price-to-book cap, the number of stocks and the cadence. QuantGPT is $49 a month and QuantGPT Pro $149, each with a 3-day free trial.