(Reuters) - In the third quarter of 2020, a group of top U.S. law firms shed more lawyers than it gained for the first time in a decade, a Monday report from Thomson Reuters Peer Monitor Index found, in a possible effort by firms to boost profits as the coronavirus pandemic drags on.

PMI, which compiles data from about 160 law firms, including many of the largest in the United States, found that those firms had 0.1% fewer lawyers in Q3 2020 than in Q3 2019. The data doesn't show the cause - such as layoffs or retirements - of that decline in headcount. The report does not identify the names of the firms.

Associates "were the preferred target of headcount reductions," the report said, and their departures have reduced costs to firms and moved work to partners who have higher billing rates.

Those changes could help make law firms "more profitable than ever" in 2020 despite demand for their services dropping 2.4% year-over-year in Q3 and the overall economy having "taken its hardest hit since the great recession," according to PMI.

PMI is part of Thomson Reuters, the parent company of Reuters news and Westlaw.

Law firms for several months have grappled with how to handle the pandemic's financial blow. Dozens of top firms slashed compensation in March and April and several furloughed or laid off staff as economic shutdowns dried up deal and trial work.

A large portion have since eased or ended pay cuts, often citing better-than-expected financial performance.

But several, including Katten Muchin Rosenman and Baker McKenzie, have since laid off staff and, in fewer cases, attorneys.