The Phillips Curve posits an inverse relationship: low unemployment pushes wages up, which pushes inflation up. In theory, the Fed faces a trade-off — can't minimize both at the same time.
In practice over the last 25 years, this relationship has been much weaker than textbooks suggest. From 2010-2019, unemployment fell from 10% to 3.5% while CPI stayed near 2% — challenging the classic model. Then 2022-2024 saw both low unemployment AND high inflation, another break from the framework.
Modern economists attribute the decoupling to anchored inflation expectations, globalization, and labor market slack indicators beyond unemployment rate. For policy watchers: the Phillips Curve is a useful frame but not a reliable predictor. Watch CPI and unemployment independently rather than expecting mechanical inverse moves.