The study looked at how oil prices can help predict the US stock market better when combined with other factors. They found that using multiple factors gives more accurate forecasts than just using oil prices alone. They also discovered that predictions based on large cap stocks may not apply to the entire market. By using a special statistical method, they were able to account for factors like persistence, endogeneity, and heteroscedasticity in their predictions. Overall, their results show that including oil prices in a multi-factor model improves forecast accuracy for both short-term and long-term predictions.