Frequency

Frequency is impressions divided by reach: the average number of times one person has been shown the ad in the window you are looking at. It is the earliest warning of fatigue, because it rises before the click rate falls — the same people are being shown the ad again while it still works on them. What counts as high depends on the audience and the ad, but for a small Indian audience on a modest budget a frequency past three in a week usually means the reachable audience is exhausted and the budget is now paying to repeat itself. Widening the audience or refreshing the creative both bring it down; raising the budget makes it worse.