Accounting firm BDO USA LLP is convinced that the road to growth leads through other firms.

BDO, one of the midtier accounting firms below the Big Four, has been aggressively trying to grow faster under Chief Executive Wayne Berson, and it believes a flurry of acquisitions is the best way to do it. BDO has acquired seven firms since Mr. Berson became CEO in November 2012—more than any other major accounting firm over the same period.

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