Union Pacific Corp. reported a 5 percent increase in fourth-quarter earnings, with improvements in the company's railroad and energy operations.

Union Pacific said it made $176 million, or $1.76 a share, in the quarter ended Dec. 31, compared with $167 million or $1.64 per share in the comparable 1989 quarter.Operating revenue rose 8 percent to $1.81 billion vs. $1.68 billion.

The company said Union Pacific Railroad had a 1 percent increase in net income to $144 million, while earnings from Union Pacific Resources rose 63 percent to $83 million. That division is involved in oil and natural gas production.

Union Pacific's real estate division, however, reported a sharp decline in income, to $6 million from $36 million in the 1989 quarter.

Overall, operating income slipped 4 percent to $332 million from $347 million in the 1989 quarter.

"We are pleased with our 1990 results and the strong performances turned in by each of our subsidiaries," said Drew Lewis, chief executive officer. "Although 1991 will be a difficult operating environment, we remain guardedly optimistic about our prospects."

For the year, Union Pacific earned a record $618 million, or $6.17 per share, compared with $595 million or $5.62 per share in 1989. Earnings per share were helped by a stock repurchase program.

Operating revenue for the year was $6.96 billion, up 9 percent over $6.39 billion in 1989.