Quality and value...

From The Small-Cap Advantage: How Top Endowments and Foundations Turn Small Stocks into Big Returns:

Factor screening on any of the aforementioned ratios suffers from a major flaw: Company value is determined by all future free cash flows discounted to the present. Rudimentary ratios fail to capture what could, should, or would happen to a company beyond the next year or two. Historical cash flows, book value, earnings, or momentum in the growth of any of these factors may not be comparable with what happens in the future for dynamic companies undergoing change. This renders these ratios useless as indicators of value. The key determinants for predicting the future earnings power of a company are actually qualitative. Factors like competitive positioning, industry growth, and the capital allocation ability of management are not adequately captured by simple ratios.