It shouldn't affect your average cost per optimisation event. However, it may affect the pacing of your ad delivery if you're using standard delivery. Your pacing will generally be smoother if you choose to be charged for a more common event (e.g. impressions). For the smoothest pacing and most efficient delivery, choose impressions. Choosing to be charged for a less common event (e.g. App Installs) could have an impact on the pacing of your ad delivery. Here's why:

Standard delivery paces the delivery of your ads with the goal of spending your budget evenly throughout your campaign. Spending your budget evenly is directly tied to when money is removed from your budget, and how much. When you choose a more common event (e.g. impressions), you'll be charged in smaller, more frequent ("smoother") increments. When you choose a lower frequency event, you'll be charged in larger, less frequent increments. It's harder to smoothly spend your budget when it decreases less predictably and in larger amounts.

Note: While we have controls in place to smooth out as much as possible the pacing of budgets charged for less common results, these controls aren't a substitute for a more common result.

The problem with having less stable delivery is that it could take us longer to gather the data required to deliver your ads as efficiently as possible. The stability that can come from getting charged for a more common result enables us to finish gathering that data sooner, which in turn enables us to start efficiently delivering your ad sooner. This could potentially lead to a higher long-term return from your ads. One potential downside to this is that your cost per optimisation event may be more volatile. (This could include your average cost per optimisation event exceeding your bid before it stabilises).

Example

Here's an example of what's at stake (and what's not) with your charge choice:

If you want to drive video views, you should choose the Video Views marketing objective and video views as your optimisation event. This tells our delivery system to show your ads to the people who we think are most likely to watch the amount of your video you specified. For your charge choice, decide whether you want:

• The smoothest pacing and delivery possible (potentially at the expense of cost per video view stability early on)
• To only be charged when someone views your video (potentially at the expense of delivery stability throughout the campaign)

If you prefer the first option, consider getting charged for impressions. If you prefer the second option, consider getting charged for video views.

Important: Remember that your choice should not have a significant effect on your average cost per video view.