Frequency
How many times, on average, each person who was reached saw the content.
Formula
Frequency = impressions ÷ reach
A frequency of 2.5 means each person reached saw the content two and a half times on average. For a launch that needs to stick, some repetition helps. Past a point, usually somewhere above 3 or 4 in a short campaign, the same people are seeing it again and new people aren't.
Across an influencer campaign, high frequency often means the creators share an audience. Five creators from the same city and niche may reach far fewer different people than their combined follower counts suggest.