Metric of corporate financial strength, basically earnings divided by assets. In theory, tells you how efficiently you're using your assets.
In practice, the easiest way to increase RONA is to sell off assets and outsource whatever function they had, which turns your business to shit if you do it enough. This might be an unfortunate manifestation of Goodhart's Law, or it might just be Control Fraud. See Crash Course, Out-Sourced Profits - The Cornerstone of Successful Subcontracting