Problems in causal loop diagrams revisited

The increasingly popular S and O notation in causal-loop diagrams has a serious flaw, which suggests it should be purged from educational, consulting, and publication practice. The flaw traces to the inability of the notation to capture correctly the influences of flows into and out of stocks, which often appear implicitly in word-and-arrow diagrams. In contrast, the older notation of plus and minus signs handles the problem well.