PTC Inc. PTC

Autodesk (ADSK) stock has lost 22% over the past month following its recent earnings release, outstripping declines in peers such as Bentley Systems (down 16.4%) while the S&P 500 barely moved. If you own the shares, the worry now is a market-wide sell-off landing on top of that loss. So how low could Autodesk stock go if the whole market turns.

PTC (PTC) and Fair Isaac are both owned for software that customers find hard to replace. PTC sells more to manufacturers it already serves, while Fair Isaac has raised the price of its mortgage credit score. Fair Isaac stock has lost 46% in a month, while PTC stock has lost 12.5%. Which of the two is gaining the firmer grip on its customers.

Autodesk (ADSK) stock has fallen 23% since late August. A $10,000 holding bought at the high is now worth about $7,700. A fall that fast pulls you toward buying, but the shares still cost more than the market on earnings. The reason to buy is that past Autodesk drops this deep mostly paid off, and the business is still sound.