Investors joined the chorus of praise yesterday after Xerox released its fourth-quarter and year-end earnings.

Mr. Seidman predicted that year-end earnings should reach $18 billion to $19 billion, a modest rise from 1990.

The move away from drug stocks comes as pharmaceutical companies report their fourth-quarter and year-end earnings.

The percentage of the cash payout that will be considered taxable depends on the year-end earnings and retained profits of the Los Angeles-based retailer, a spokesman said.

LEAD: The Mellon Bank Corporation said it expected to post lower year-end earnings next week, reflecting higher loan losses and the bank's decision to increase its reserves.

The company said that year-end earnings were also affected by $463 million in one-time charges for restructuring and costs related to the recall of the Benlate DF fungicide.

First, many companies report their financial year-end earnings in October.

USAir Group Inc. expects its year-end earnings to exceed Wall Street expectations, the airline said on Tuesday.

The K Mart Corporation said it expected lower 1990 fourth quarter and year-end earnings because of disappointing apparel sales and margins in November and December.

The new rule has produced a stream of details that otherwise would have been buried deep in quarterly or year-end earnings reports.