Updated from 11:18 a.m. EDT

The listless trading that characterized the second quarter and helped contribute to weaker-than-expected earnings at Merrill Lynch ( MER) is likely to remain in place throughout the third quarter, some analysts say, as retail and institutional traders sit out the summer months.

Low levels of volume and volatility sent Merrill's trading revenue down 40% sequentially in the second quarter, with revenue from both global equity and global debt markets falling sharply. As a result, Merrill reported earnings that missed analysts' estimates.

Unfortunately for Merrill and other Wall Street brokers, some experts say things aren't likely to get much better over the next three months.

"The summer is typically a less-volatile time, there's less trading volume so one would expect the trends that we saw in June to at least continue, if not even get a little worse as we go into July and August," said Ken Worthington, an analyst at CIBC World Markets.

Worthington said volatility in fixed-income markets has ticked up "a little bit" this month but is still well below levels seen in April and May. Equity volatility has also risen slightly in July from the end of June but remains far below the levels seen in most of the second quarter. "My guess is people will start to model-in down earnings for the September quarter," he said.

Analysts surveyed by First Call are expecting Merrill to earn $1.09 in the third quarter. In the three months ended June 30, the company earned $1.08 billion, or $1.06 a share, compared with earnings of $977 million, or $1 a share, in the same period last year.

Revenue rose less than 1% from a year ago to $5.30 billion. Analysts polled by Thomson First Call were forecasting earnings of $1.09 a share on revenue of $5.71 billion.

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