The market effects of the Covid-19 outbreak have thrown off machine learning models that historically relied on correlations between different types of datasets—correlations that are no longer making sense. “We are living through an era now where all of the correlations [in machine learning models] sort of broke overnight,” says David Cox, IBM director of the MIT–IBM Watson AI Lab. 

For example, before the onset of the pandemic, customers who shopped at an upscale grocery store might also have