On March 9, as the S&P 500 slid nearly 8% amid coronavirus panic, market participants endured whiplash, including Kevin Welch, managing director of investor services at New York-based Brown Brothers Harriman.

Welch and his team had a very small window at the end of the day to strike a net asset value (NAV) for their clients, even as the number of price anomalies detected soared. With the help of supervised machine learning models that were put into place a few years ago, they were able to do it