Public companies are less likely these days to have to restate their earnings or other financial figures. Clients of PricewaterhouseCoopers LLP are bucking this trend recently, new data show.

The Big Four audit firm has had a streak of accounting problems surface recently at U.S. companies it audits, including an uptick in high-profile restatements. Its clients account for three of the five biggest restatements so far this year, measured by cumulative impact on net income, according to a Wall Street Journal analysis of data from research firm Audit Analytics.

How the analysis was done:

The Journal analyzed Audit Analytics data through 12/12/2019. The number of revisions for 2019 to date is expected to increase, as more financial statements affecting this year are filed. An audit firm was counted as connected to a client’s restatement if it signed the audit opinion for the financial period(s) in which the misstatement occurred. In some cases, more than one audit firm is connected to a single restatement.

Companies audited by PwC have been more prone over the last couple of years than clients of the other Big Four firms to do the most serious type of restatement, the analysis found. These involve a company alerting clients to a problem and reissuing its financial statements.

Since the start of 2018, PwC clients have done 15 of these “Big R” restatements, more than the combined total of 11 for companies audited by Deloitte LLP, Ernst & Young LLP and KPMG LLP, according to the analysis.

In the last three months alone, serious accounting problems disclosed by PwC clients include a restatement of past earnings by toy maker Mattel Inc. ; foreign currency-related errors that medical-supplies company Baxter International Inc. said might force it to restate results; and a federal investigation into the accounting practices of sportswear maker Under Armour Inc.

“PwC shows up in an awful lot of these recent restatement situations,” said Don Bilson, an analyst at investment research firm Gordon Haskett Research Advisors. “We now think of PwC as a low-probability risk factor that investors should think about, especially in cases where the accounting smells creative.”

A PwC spokeswoman said in response to the Journal’s analysis that “audit quality remains a top priority” at the firm. Financial restatements and revisions “are not the sole—or even primary—measure of audit quality,” the spokeswoman said. She added that on average 99.4% of the more than 1,600 audits conducted by PwC US during each of the last three fiscal years didn’t involve a financial restatement.

PwC also stands out for another type of restatement. These involve a company quietly updating past financial statements without having to alert investors. Although these “Little r” revisions are designed to correct minor accounting problems, recent research found some were associated with significant share-price falls, the Journal reported this month.

The annual total of “Little r” revisions by companies audited by PwC has fallen sharply since 2015. But the total in each of the past five years is still significantly more than for clients of any other Big Four firm, the Journal’s analysis found.

In total, PwC-audited clients have issued 425 restatements—“Big R” and “Little r” combined—since the start of 2015. That is almost twice as many as any other Big Four firm, the analysis found.

The difference isn’t due to market share. PwC clients account for just under a quarter of all U.S. public companies audited by Big Four firms, Audit Analytics data show.

Charles Mulford, accounting professor at the Georgia Institute of Technology, said the responsibility for each restatement depended on the facts and circumstances. But he added that the recent high levels of PwC-client restatements was a “tag on them—I’m bothered by it.”

Granted, a run of “Big R” restatements among clients could also be just a statistical quirk. “Go into any casino and you can see clustering in random numbers,” said Jim Peterson, a lawyer and former partner at accounting firm Arthur Andersen LLP.

Nonetheless, all the Big Four firms cite the percentage of their clients doing “Big R” restatements in reports on the quality of their audits. Ernst & Young, for example, says it monitors these restatements for “any trends that require additional action or changes to our system of quality control.”

The Big Four firms don’t cite “Little r” revisions as a benchmark. But Douglas Carmichael, professor of accountancy at Baruch College, CUNY, said, “Both ‘Big R’ and ‘Little r’ restatements are indicators of audit quality.”

He added that it was the auditor’s job to “detect a relatively high percentage of material misstatements [and] failure to do that is an indication of lack of audit quality.”

Spokesmen for Deloitte, Ernst & Young and KPMG declined to comment.

Auditors play an important role advising clients on whether restatements are needed and, if so, of what type.

At an accounting conference in Washington, D.C., last week, a senior Securities and Exchange Commission official discussed how companies should decide between “Big R” and “Little r” restatements. “What I would say to that [question] is work with your auditor,” said Kyle Moffatt, the chief accountant in the SEC’s division of corporation finance, which polices financial reporting.

Auditors can look for ways to avoid disclosing errors, particularly in situations where there is scope for interpretation, the Journal previously reported, citing whistleblower allegations that a former PwC auditor helped Mattel try to bury an accounting problem. Mattel at the time said the accounting error was an honest mistake, while PwC said “integrity is at the heart of who we are and how we operate.”