Hagler Bailly Inc., an Arlington management and economic consulting firm, reported decreased net income as the company continues to try to decrease costs and boost revenue.

Net income for the third quarter ended Sept. 30 was $1.4 million (8 cents a share), compared with $4 million (24 cents) in the same period in 1998. Revenue was $48.1 million, compared with $46.5 million.

For the first nine months of the year, the company earned $4 million (23 cents) on revenue of $132.9 million, compared with $11.5 million (66 cents) on revenue of $132.1 million.

"Third-quarter results were in line with our revised estimates," said chief executive William E. Dickenson. "The company continues to take steps to improve our profitability in terms of increasing utilization rates, implementing cost-saving measures and strengthening revenue streams."

The company beat Wall Street estimates by a penny. Hagler Bailly's stock closed at $6.25 yesterday, down 25 cents.

* Corporate Executive Board Co., a Washington provider of research to major corporations, said its pro forma net income grew by more than 111 percent, to $2.92 million (18 cents a share), on revenue of $18.4 million. Third-quarter 1998 pro forma net income was $1.38 million (9 cents) on revenue of $13.7 million.

Revenue for the first nine months of 1999 rose 33 percent, to $50.8 million, from $38.2 million for the comparable period in 1998. Pro forma net income increased to $7.4 million (46 cents) from $4.2 million (28 cents).

* Federal Realty Investment Trust, a Rockville company that owns strip shopping centers, reported that results improved in the third quarter as rents increased and administrative expenses fell after an internal revamping last year that reduced and rearranged its work force.

Funds from operations, the most widely followed gauge of real estate companies' results, rose 14 percent, to $24.4 million, from $21.43 million in the same quarter last year; on a per-share basis, it increased 11 percent, to 60 cents from 54 cents. Funds from operations is a financial measure that adds back charges for property amortization and depreciation that otherwise reduce net income.

Revenue in the quarter was $67.26 million, up 14 percent from $59 million. Net income was $14.19 million (40 cents a share) compared with $7.52 million (14 cents).

In the first nine months of the year, funds from operations was $72.28 million ($1.78), up 14 percent from $63.62 million ($1.59) in the same period a year earlier. Revenue rose 12 percent, to $195.03 million from $173.58 million. Net income rose 7 percent, to $34.56 million from $32.18 million.