While in the past Google went over the daily budget some days (by up to 20 percent), it says in the industry press that the limit is now 100 percent.
Some questions
1)
Does the system take from a campaign that doesn't hit its budget to fund a campaign out of budget?
Campaign 1: budget $200. Actual spend most days $50. Impression share high.
Campaign 2: budget $500. Actual spend $500 every day. Hits limit. Impression share low.
Will the Google system say, hey they aren't spending their budget on Campaign 1, so we will feel free to use that $150 per day on Campaign 2?
2)
The overspend on any day is counterbalanced by lower spending on other days but how long a period is considered.
For instance
Campaign 1: budget $200. Avg position 5.2
Let's say spending is low because of the low avg position. Let's say in the first 29 days of the month we spend $40/day. Total spending is $1160 through first 29 days.
Monthly budget is $6000 or $6200.
Now on the 30th of the month we raise bids but do not raise the budget. We get to avg position 1.3
Budget is still $200/day but we are way below budget for the month.
I am afraid Google's system will feel free to spend $4200 on the 30th, to make up for low spending during the first 29 days.
