Consolidation among four of the five largest health insurers in the United States is unlikely to jeopardize UnitedHealth Group Inc.'s position at the top of the industry, Moody's Investors Service Inc. said in a report released on Thursday. UnitedHealth's diverse portfolio of business lines, consistent financial performance and brand recognition should help the Minnetonka, Minnesota-based health insurer retain its competitive edge as rival insurers Anthem Inc. and Aetna Inc. each seek to grow their market share by merging with Cigna Corp. and Humana Inc., respectively, Moody's analysts said in the report.