The correlation between stock and bond yields changes when bond yields are low, becoming negative. This happens because low bond yields signal economic risks like deflation, causing stock and bond prices to move in opposite directions. The FED model, which predicts future returns, relies on a positive correlation, leading to mixed results. By studying G7 markets, researchers found evidence of this correlation switch based on bond yield levels. This finding can help market practitioners with timing decisions and academics studying market interrelations.