U.K. companies bought by private- equity firms become less productive than their peers, according to a study by academics at three British universities.

Researchers at Warwick Business School, Cardiff University and Loughborough University profiled the 105 U.K.-traded firms taken private from 1997 to 2006 and examined their performance over 10 years, six before the buyout and four after, against those not owned by private equity.

The report found that the performance of the private- equity-backed companies, measured by revenue per employee, worsened under their tenure with an average revenue gap of 89,000 pounds ($136,600) against the control group after four years compared with 29,000 pounds in the year before the acquisition.

“What we found was the promised productivity gains of a takeover rarely materialized,” Geoffrey Wood, professor of international business at Warwick Business School, said today in an e-mailed statement. “Rather, there was evidence of private- equity buyouts reducing the number of workers and squeezing wages, without making the firm more efficient.”

Wood attributed the performance gap to private-equity firms finding “it more difficult to cost the worth of a firm’s human assets, and their combined knowledge and capabilities.”

The report also found deeper cutbacks among the private- equity-backed companies, with 59 percent reducing the workforce in the year after acquisition compared with 32 percent in the control group.

Editors: Steve Bailey, Jon Menon