Grounding rate

The percentage of answers that returned sources. Grounding means the engine retrieved web pages before answering instead of relying only on what the model already knows.

For Google AI Overview, searches where no overview appeared are excluded here, since there is no answer to grade; those same searches still count against Visibility, where a definite absence is exactly the signal.

An answer with no sources cannot point to anyone, you or a competitor, so this number is the context for Influence: it tells you how many answers were even eligible to use you as a source.