That’s because the correlation between crude oil and stocks has not been stable over time. For several decades prior to 2000, for example, that correlation was negative, as you can see in the chart below. During those decades, higher oil prices in a given month led to below-average stock-market returns in the subsequent month.

This article will be updated throughout the day, so check back often for more daily updates. The plunge in oil prices earlier this week gave way to a slight rebound in prices Wednesday. Per-barrel prices of both WTI crude oil and Brent crude,