An advertiser implements target cost-per-acquisition (CPA) bidding and notices that the campaigns are receiving fewer conversions. What could help increase the number of conversions?
Increase the target CPA bid
Set the campaign budget to a 30-day cycle
Specify the bid amount for each individual campaign
Try a different automated bid strategy
This is the average amount you’d like to pay for a conversion. The target CPA you set may influence the number of conversions you get. Setting a target that is too low, for example, may cause you to forgo clicks that could result in conversions, resulting in fewer total conversions. If your campaign has historical conversion data, AdWords will recommend a target CPA. This recommendation is calculated based on your actual CPA performance over the last few weeks. We’ll exclude performance from the last few days to account for conversions that may take more than a day to complete following an ad click. You can choose whether to use this recommended target CPA or to set your own.
Your target CPA might be too low. You may want to compare your target CPA to the historical average CPA of your campaign. If your target CPA is significantly below your historical average CPA, your target CPA may not be attainable while maintaining reasonable levels of traffic, and you should consider raising your target.
Read more here: //support.google.com/adwords/answer/6385155?hl=en