Bid adjustments at location level allow you as an advertiser to bid up, or down, depending on the performance or goals, of a particular location target.
This will allow you to show your ads more, or less frequently and, control the investment and cost per result of a particular location within your campaigns.
Bid adjustments are set by percentages.
For example, a campaign targeting the whole of the United Kingdom, that performs well in a particular city, "Birmingham" with a max CPC (cost-per-click) bid of £1.
To show your ad to more customers in Birmingham, you can increase your bid by 20% for searches on mobile devices, resulting in a final bid amount of £1.20.
Here are the maths:
Starting bid: £1
Location bid adjustment: £1 + (+20%) = £1.20
Resulting bid for searches in Birmingham: £1.20
In another example, let’s say that you have a £1 bid and would like to decrease it. To adjust it to £0.80, select Decrease by 20%.
You can apply location bid modifiers at the campaign level and increase or decrease your bids by -90% up to +900%.